SLIDING FILM, METHOD OF PRODUCING SAME, SLIDING MEMBER, AND METHOD OF PRODUCING SAME

Abstract

Provided are a sliding film that has desired surface roughness and surface shape and contains a hard carbon material as a main component, a method of producing the sliding film, a sliding member, and a method of producing the sliding member. A diamond film has a smooth transfer surface. The transfer surface is a sliding surface. A sliding member includes an adhesive layer for bonding the diamond film on a base. The deposited diamond film is removed from a substrate. The transfer surface on the side of the substrate of the diamond film is set as the sliding surface. A deposited surface opposite to the transfer surface is attached and fixed onto the base via the adhesive.

Claims

1. A sliding film, having a smooth transfer surface, the transfer surface being a sliding surface, the sliding film containing a hard carbon material as a main component.

2. The sliding film according to claim 1, n wherein the hard carbon material comprises diamond.

3. The sliding film according to claim 1, wherein a roughness of a surface opposite to the sliding surface is larger than a roughness of the sliding surface before use.

4. A method of producing a sliding film, comprising the steps of: depositing a sliding film on a smooth surface of a substrate, the sliding film containing a hard carbon material as a main component; and removing the sliding film, deposited in the deposition step, from the substrate.

5. The method of producing a sliding film according to claim 4, wherein in the removing step, the sliding film is removed by dissolving the substrate.

6. The method of producing a sliding film according to claim 4, wherein at least one of a convex part and a concave part is formed in the substrate.

7. The method of producing a sliding film according to claim 4, wherein the hard carbon material comprises diamond.

8. The method of producing a sliding film according to claim 4, wherein a roughness of a surface of the sliding film opposite to the substrate is larger than a roughness of the surface of the substrate.

9. A sliding member, comprising: a base; a sliding film having a sliding surface and containing a hard carbon material as a main component; and an adhesive layer for bonding the sliding film to the base.

10. The sliding member according to claim 9, wherein the hard carbon material comprises diamond.

11. The sliding member according to claim 9, wherein a surface roughness, on a side of the adhesive layer, of the sliding film is larger than a surface roughness, on a side of the sliding surface, of the sliding film.

12. The sliding member according to claim 9, wherein the sliding surface is a transfer surface.

13. The sliding member according to claim 9, wherein the adhesive layer has a smaller Young's modulus than each of the base and the sliding film in a state where the adhesive layer bonds and fixes the base and the sliding film.

14. A method of producing a sliding member, comprising the steps of: removing a sliding film deposited in a deposition step from a substrate, the sliding film containing a hard carbon material as a main component; and bonding the sliding film removed in the removing step to a base.

15. The method of producing a sliding member according to claim 14, wherein in the deposition step, the sliding film containing the hard carbon material as the main component is deposited on a smooth surface of the substrate.

16. The method of producing a sliding member according to claim 14, wherein in the removing step, the sliding film is removed by dissolving the substrate.

17. The method of producing a sliding member according to claim 14, wherein at least one of a convex part and a concave part is formed in the substrate.

18. The method of producing a sliding member according to claim 14, wherein the hard carbon material comprises diamond.

19. The method of producing a sliding member according to claim 14, wherein a roughness of a surface of the sliding film opposite to the substrate is larger than a roughness of the surface of the substrate.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0073] FIGS. 1A to 1E are cross-sectional views showing a first embodiment of a sliding member and a method of producing the sliding member according to the present invention, in which FIG. 1A is a cross-sectional view of a substrate, FIG. 1B is a cross-sectional view showing a state of a diamond film deposited on the substrate, FIG. 10 is a cross-sectional view showing a state of the diamond film removed from the substrate, FIG. 1D is a cross-sectional view showing a state in which the diamond film is bonded to the base, and FIG. 1E is a cross-sectional view of a sliding member.

[0074] FIGS. 2A and 25 are reference cross-sectional views showing a state of polishing a sliding surface, in which FIG. 2A is a cross-sectional view of a state of polishing by co-grinding, and FIG. 2B is a cross-sectional view of the sliding member polished.

[0075] FIGS. 3A to 3E are cross-sectional views showing a second embodiment of a sliding member and a method of producing the sliding member according to the present invention, in which FIG. 3A is a cross-sectional view of a substrate, FIG. 3B is a cross-sectional view showing a state of a diamond film deposited on the substrate, FIG. 3C is a cross-sectional view showing a state of the diamond film removed from the substrate, FIG. 3D is a cross-sectional view showing a state in which the diamond film is bonded to the base, and FIG. 3E is a cross-sectional view of a sliding member.

[0076] FIGS. 4A and 4B are reference cross-sectional views showing a recessed groove formed in the sliding surface by laser machining, in which FIG. 4A is a cross-sectional view showing a state of laser machining, and FIG. 45 is a cross-sectional view of a sliding member subjected to the laser machining.

[0077] FIG. 5 is a cross-sectional view showing a third embodiment of a sliding member according to the present invention.

DESCRIPTION OF EMBODIMENTS

[0078] Modes for carrying out a sliding film, a method of producing the sliding film, a sliding member and a method of producing the sliding member according to the present invention will be described below based on embodiments. In the following description, the terms up, down, right, and left will be defined as the upward, downward, rightward, and leftward directions on the plane of the paper of FIGS. 1A to 1E.

[0079] The sliding film is a film deposited using a hard carbon material as a main component. Examples of the hard carbon material include diamond as a crystal made of SP.sup.3 bonded carbon, a Diamond-Like Carbon (DLC) mainly made of an amorphous SP.sup.3 bonded carbon, etc. In the description below, a diamond film deposited using a diamond as a main component, which is physically and chemically more stable, will be explained by way of example.

[0080] Here, the method of producing the diamond film is not particularly limited, but a high-pressure synthesis method, a vapor-phase synthesis method, and the like are known. In terms of its deposition, the vapor-phase synthesis method is preferable. Examples of the vapor-phase synthesis method suitable for use can include plasma CVD, thermal filament CVD, and microwave plasma CVD, etc.

[0081] The substrate on which the diamond film is grown is made using Si (silicon), SiC (silicon carbide), or WC (tungsten carbide). On the substrate, diamond is formed by heteroepitaxial growth and further by polycrystalline growth with high orientation. When using these kinds of substrates, the substrate is desirably subjected to pretreatment, such as scratching, a bias electric field, and a seeding treatment, as is well-known.

[0082] Note that a single crystalline diamond may be used as the substrate, and then on this substrate, diamond may be formed by homoepitaxial growth.

[0083] Gas containing carbon and preferably gas obtained by diluting methane with hydrogen can be used as raw material gas. A small amount of oxygen, carbon monoxide and carbon dioxide may be added to the raw material gas as needed. The raw material gas is decomposed by plasma, heat, or the like, and active species in the gas phase and the like, created from the raw material gas, are crystallized on a heated substrate, thereby depositing a diamond film. Hydrogen atoms, created and dissociated from the raw material gas, act to etch carbon in the non-diamond structure, whereby only a diamond phase is obtained.

First Embodiment

[0084] In the following, the first embodiment will be described with reference to FIGS. 1A to 1E.

[0085] <Step (a)>

[0086] A substrate 10 made of SiC and having a predetermined flat surface 11 is prepared.

[0087] <Step (b)>

[0088] Diamond is heteroepitaxially grown from the raw material gas by the thermal CVD, whereby a diamond film 20 is deposited on the flat surface 11 of the substrate 10.

[0089] <Step (c)>

[0090] After the deposition, the substrate 10 or its surface is dissolved by dry etching using fluorine-based etching gas, thereby removing the diamond film 20 from the substrate 10.

[0091] <Step (d)>

[0092] An adhesive 40 (adhesive layer) is applied onto a base 30, which configures a structure body of a sliding member 50. The diamond film 20 is then turned upside down and then attached onto the adhesive 40 by pressing a deposited surface 22, which is positioned as an upper surface during the deposition, toward the lower side, i.e., toward the side of the base 30.

[0093] <Step (e)>

[0094] The sliding member 50 that has a sliding surface 21 (transfer surface 21) formed by transfer can be obtained.

[0095] In step (a), the flat surface 11 is a smooth surface. The smoothness of the surface is defined by surface roughness, including Rmax (maximum height), Rz (ten-point average roughness), Ra (center line average roughness), in conformity with JIS 0601-1976. In the first embodiment, the predetermined flat surface 11 has a smooth surface. For example, the smooth surface is defined as a surface with an Ra of 1.6a or less. In step (c), the transfer surface 21 as the lower surface of the diamond film 20, removed from the substrate 10, is one to which the flat surface 11 of the substrate 10 is transferred. Thus, the Ra of the transfer surface is substantially equal to the Ra of the flat surface 11, i.e., 1.6a. Meanwhile, in the diamond film 20, a deposited surface 22 as the upper surface thereof is much rougher than the transfer surface 21. Note that for convenience of explanation, in FIGS. 1A to 1E, the surface of the deposited surface 22 is drawn exaggeratedly. Further, means for removing the diamond film 20 from the substrate 10 may also be means other than dry etching, for example, means for physically peeling off the diamond film. Note that for dry etching or wet etching, an etchant that can dissolve only the substrate 10 without dissolving the diamond film 20 is preferably used.

[0096] Further, the adhesive 40 for use in step (d) is one that has a smaller Young's modulus than each of the base 30 and the diamond film 20 in a state where the adhesive 40 bonds and fixes the diamond film 20 to the base 30 in step (e) (in a state where the adhesive 40 is being hardened). Moreover, the structure body is a member that configures a machine element of a machine and equipment, for example, like a housing and a rotary shaft. The base 30 configures a part of the structure body.

[0097] As mentioned above, since in the diamond film 20, the sliding surface 21 is the transfer surface 21, the sliding surface 21 has high accuracy for the surface roughness and surface shape. Because of this, even when using the diamond film 20 that contains, as a main component, diamond which is hard and difficult to process, the accuracy of the surface roughness and surface shape of the diamond film is high.

[0098] Furthermore, before the use, the roughness of the deposited surface 22, positioned on the opposite side to the sliding surface 21, is larger than the roughness of the sliding surface 21. That is, since the smooth surface is set as the sliding surface 21, the need for a process, such as lapping, can be eliminated or lessened. That is, as shown in FIGS. 2A and 2B, the present embodiment can eliminate or lessen the need for a process of producing a conventional sliding member 150, i.e., a process of forming a flat sliding surface 122 by co-grinding and polishing the deposited surface 122 of the diamond film 120 deposited on a substrate 130 as a base by use of a polishing diamond film 140.

[0099] Since the diamond film 20 is fixed to the base 30 by bonding with the adhesive 40, as long as the base is made of a material that enables bonding of the diamond film by the adhesive 40, the diamond film can be fixed to the base. There is a wide range of choices for the material of the base 30 to which the diamond film 20 is fixed. In other words, the diamond film 20 can be fixed, regardless of the material of the substrate 10 on which the diamond film 20 is deposited. Note that the diamond film 20 to be bonded to the base 30 may be formed at one or a plurality of members in the surface direction of the base 30. The diamond film 20 can be formed over the plurality of members, thereby easily forming a sliding surface with a wider area.

[0100] Further, in the diamond film 20, the roughness of the deposited surface 22 on the side of the adhesive 40 is larger than the surface roughness of the sliding surface 21, and the deposited surface 22 has a wide surface area that is in contact with the adhesive 40. Thus, the diamond film 20 can be firmly fixed to the base 30. Moreover, the deposited surface 22 on the side of the adhesive 40 may be rough, thereby making it possible to enhance a film deposition rate. Meanwhile, since the sliding surface 21 is the transfer surface 21, the accuracy for the surface roughness and surface shape becomes high.

[0101] Furthermore, the adhesive 40 has a smaller Young's modulus than each of the base 30 and the diamond film 20 in a state where the adhesive 40 bonds and fixes the base 30 and the diamond film 20. Thus, during sliding operation, an intermediate layer which is made of the adhesive 40 serves as the so-called buffer material. That is, even when the base 30 is deformed by thermal expansion, the intermediate layer of the adhesive 40 can act as the buffer to reduce the influence of a force acting between the base 30 and the diamond film 20.

Second Embodiment

[0102] Next, a sliding member representative of the second embodiment will be described with reference to FIGS. 3A to 3E. The second embodiment differs from the first embodiment mainly in that a concave part is provided in the sliding surface 21. Note that the description of the configuration in the second embodiment that is the same as and overlaps with that in the first embodiment will be omitted.

[0103] As shown in FIGS. 3A to 3E, a convex part 13 with a trapezoidal cross section is formed in the substrate 10 to protrude upward from the flat surface 11 of a base part 12. The diamond film 20 is deposited on the substrate 10, whereby a concave part 24 is formed along the shape of the convex part 13 on the side of the transfer surface 21 (sliding surface 21) of the diamond film 20. In this way, the concave part 24 can be provided to impart a specific function (for example, a function of holding a lubricant) to the sliding surface 21. It is preferred that the depth of the concave part 24 is shallower (shorter) than the thickness of a base part 23 of the diamond film 20 because the mechanical strength of the diamond film 20 can be ensured.

[0104] As mentioned above, the convex part 13 is formed in the substrate 10, and the concave part 24 is formed by transferring the convex part 13 to the diamond film 20, so that the concave part 24 with a desired shape can be easily formed. That is, as shown in FIGS. 4A and 43, the present embodiment can eliminate the need for a process of producing the conventional sliding member 150, i.e., a process of forming a concave part 124 by applying laser irradiation 160 to a deposited surface 122 of a diamond film 120, deposited on the substrate 130 as the base.

[0105] As an example it has been described above that the convex part 13 is formed in the substrate 10, and then the concave part 24 is transferred to the diamond film 20. However, a concave part may be formed in the substrate 10, and then a convex part may be formed in the diamond film 20, thereby imparting another specific function to the sliding surface 21. Further, both the convex part and the concave part may be provided to impart other specific functions to the sliding surface.

Third Embodiment

[0106] Next, a sliding member representative of the third embodiment will be described with reference to FIG. 5. The third embodiment differs from the first embodiment mainly in the shape of the base 30 at which the diamond film 20 is provided. Note that the description of the configuration in the third embodiment that is the same as and overlaps with that in the first embodiment will be omitted.

[0107] As shown in FIG. 5, the base 30 has a substantially inverted J-shaped cross section in which a long-side part 31 and a short-side part 32 are coupled together. The diamond film 20 is attached along and fixed to the upper surface of the long-side part 31. In this way, the diamond film 20 is attached and fixed to the base 30 with the adhesive 40, so that the diamond film 20 can be disposed in a concave space formed by the long-side part 31 and the short-side part 32. That is, when the diamond film 20 is intended to be formed by deposition directly on the upper surface of the long-side part 31, the diamond film 20 cannot be deposited in a region A because it is blocked by the short-side part 32. However, since the diamond film 20 is attached to the base 30 by the adhesive 40, the diamond film 20 can also be provided in the region A, which leads to a high degree of flexibility in the shape of the base 30.

[0108] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, specific configurations are not limited to these embodiments and various modifications and additions can be made to be included in the present invention without departing from the gist of the present invention.

[0109] Although in the above-mentioned embodiments, the surface of a part of the base 30 where the diamond film 20 is attached is flat by way of example, the surface may be curved. In this case, when attaching the flat-shaped diamond film 20 to the base 30, the diamond film 20 may be attached by being deformed along the surface of the base 30. Alternatively, a curved diamond film 20 is obtained by depositing on a curved substrate 10, which has the shape along the surface of the base 30, and then the curved diamond film 20 may be attached and fixed to the surface of the base 30. In the former case, since the diamond film 20 has the flat shape, the manufacture of the diamond film 20 is easy. Meanwhile, in the latter case, since the diamond film 20 is not deformed, no internal stress occurs substantially in the diamond film 20 attached and fixed to the base 30, which is preferable.

REFERENCE SIGNS LIST

[0110] 10 Substrate [0111] 11 Flat surface [0112] 13 Convex part [0113] 20 Diamond film (Sliding film) [0114] 21 Transfer surface, sliding surface [0115] 22 Deposited surface [0116] 24 Concave part [0117] 30 Base [0118] 40 Adhesive (Adhesive layer) [0119] 50 Sliding member