Sliding parts

Abstract

Provide is a sliding component capable of suppressing temperature increases of sliding surfaces.　A sliding component 10, 20 having sliding surfaces 11, 21 that slide in a relative manner, wherein a base material 22 of the sliding component 20 is directly coated with a thin film 30 composed mainly of glass-like carbon, and the sliding surface 21 is formed from the graphite film 30.

Description

Technical Field

[0001] The present invention relates to sliding parts that slide relative to each other. For example, it is used for sliding parts used in shaft sealing devices that seal the rotating shafts of rotating machines in the automotive, general industrial machinery, or other sealing fields, or for sliding parts used in bearings of machines in the automotive, general industrial machinery, or other bearing fields.

Background Art

[0002] Sliding parts have a sliding surface that slides relative to the sliding surface of the mating part, and are used as components of bearings that support shafts that rotate or reciprocate, or shaft sealing devices that prevent leakage of the fluid to be sealed. As a shaft sealing device for preventing leakage of the fluid to be sealed, for example, a mechanical seal includes a pair of annular sliding parts that rotate relative to each other and whose sliding surfaces slide against each other. For example, the sliding part shown in Patent Document 1 includes a base material formed of SiC, an adhesive layer on the sliding surface side of the base material, and a sheet-like member of glassy carbon attached to the base material via the adhesive layer, so that wear resistance is obtained by the glassy carbon present on the sliding surface of the sliding part.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in sliding parts such as those in Patent Document 1, the frictional heat generated by relative sliding with the sliding surface of the mating part stays in the adhesive layer with low thermal conductivity and the sheet-like member of glassy carbon on the sliding surface side of this adhesive layer and is difficult to dissipate heat. There is a problem that the temperature of the sliding surface rises, leading to an increase in the friction coefficient and the occurrence of cracks.

[0005] The present invention has been made paying attention to such problems, and an object thereof is to provide a sliding part capable of suppressing a temperature rise of a sliding surface.

Means for Solving the Problems

[0006] In order to solve the above problems, the sliding part of the present invention is a sliding part having sliding surfaces that slide relative to each other, a thin film mainly composed of glassy carbon is directly coated on the base material of the sliding part, and the sliding surface is composed of the thin film. According to this, since a thin film mainly composed of glassy carbon is directly coated on the base material of the sliding part, frictional heat generated by relative sliding with the sliding surface on the other side is directly transferred from the thin film to the base material, so that a temperature rise of the sliding surface can be suppressed. Further, since the thin film is mainly composed of glassy carbon, it has excellent wear resistance and is difficult to bite even in a poor lubrication state.

[0007] The thin film may mainly contain glassy carbon and may contain graphite mixed therein. According to this, a part of the graphite mixed in the thin film directly coated on the base material enters the unevenness of the surface of the base material, so that the adhesion of the thin film to the base material can be enhanced.

[0008] The thin film may contain a filler having a size equal to or less than the film thickness of the thin film. According to this, the sliding surface is added with the function of the filler, and even a thin film with a thin film thickness is difficult for the filler to fall off, and the filler can be suppressed from protruding from the sliding surface, so that it is difficult to damage the sliding surface on the other side by friction.

[0009] The thin film may contain a high thermal conductivity filler having a higher thermal conductivity than the glassy carbon constituting the thin film. According to this, since the thin film mainly composed of glassy carbon contains a high thermal conductivity filler, the thermal conductivity of the sliding surface can be increased, so that frictional heat is more easily transferred from the thin film to the base material.

[0010] The thin film may contain a low-friction filler having a coefficient of friction smaller than that of the glassy carbon constituting the thin film. According to this, since the thin film mainly composed of glassy carbon contains the low-friction filler, the lubricity of the sliding surface can be enhanced.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0012] Modes for carrying out the sliding component according to the present invention will be described below based on examples.

Examples

[0013] The sliding component according to the example will be described with reference to FIGS. 1 to 5. In this example, a form in which the sliding component is a mechanical seal will be described as an example. Further, the low-pressure fluid side with the inner diameter side of the sliding component constituting the mechanical seal as the leakage side and the high-pressure fluid side (sealed gas side) with the outer diameter side as the fluid to be sealed will be described.

[0014] The mechanical seal for general industrial machinery shown in Fig. 1 is an inside type that seals the gas to be sealed that tends to leak from the outer diameter side to the inner diameter side of the sliding surface in a non-lubricated environment where no liquid is interposed between the sliding surfaces, that is, in a dry environment.

[0015] The mechanical seal is mainly composed of a rotating seal ring 20 as a sliding part and a stationary seal ring 10 as a sliding part. The rotating seal ring 20 is in an annular shape and is provided in a state where it can rotate together with the rotating shaft 1 via a sleeve 2 on the rotating shaft 1. The stationary seal ring 10 is in an annular shape and is provided in a non-rotating state and axially movable state on a seal cover 5 fixed to the housing 4 of the equipment to be attached. By the spring 6 biasing the stationary seal ring 10 axially, the sliding surface 11 of the stationary seal ring 10 and the sliding surface 21 of the rotating seal ring 20 are in close sliding contact with each other. Also, the space between the rotating seal ring 20 and the sleeve 2 is sealed by a gasket 7, and the space between the stationary seal ring 10 and the seal cover 5 is sealed by an O-ring 8.

[0016] The stationary seal ring 10 and the rotating seal ring 20 in this embodiment are formed of SiC (silicon carbide). Note that the stationary seal ring 10 and the rotating seal ring 20 are not limited to being composed of the same material and may be composed of different materials.

[0017] As shown in Fig. 2, the rotating seal ring 20 is configured by directly coating a thin film 30 on an SiC substrate 22 as a base material. That is, the substantial sliding surface 21 in the rotating seal ring 20 is constituted by the surface 30a of the thin film 30. Note that in this embodiment, it is assumed that no thin film is formed on the sliding surface 11 of the stationary seal ring 10 as the mating sliding surface (see Fig. 4).

[0018] In this embodiment, the sliding surface 21 is described as being such that the thickness of the thin film 30 is thicker than the surface roughness of the SiC substrate 22, and the entire surface of one axial end face 22a of the SiC substrate 22 is covered with the thin film 30, as will be described later. However, the present invention is not limited to this. For example, by forming the thin film 30 to be thin, the sliding surface 21 may be such that part of the end face 22a of the SiC substrate 22, such as the top of the mountain on the surface, is exposed and not covered with the thin film 30.

[0019] Furthermore, since the thin film 30 is directly coated on the SiC substrate 22, there is no need to take the time to form an intermediate layer, as compared to when an intermediate layer is used, and there are no restrictions on the conditions of use that are tailored to the intermediate layer.

[0020] The term "thin" in "thin film" means that the film is thinner than the substrate.

[0021] In addition, in this embodiment, the thin film 30 has a structure based on a carbon atom skeletal structure containing glassy carbon as the main component, and the thin film 30 contains a high thermal conductivity filler 40 and a low friction filler 41 as fillers.

[0022] Glassy carbon is a type of carbon material that is mainly composed of carbon atoms and is non-graphitized carbon, and is a substance that can be analyzed by Raman spectroscopy and the like.

[0023] Specifically, the thin film 30 of this example is a thin film mainly composed of glassy carbon, i.e., a thin film having a composition in which the characteristics of the glassy carbon component in the skeletal structure of carbon atoms on the surface are prominently exhibited. Note that some of the carbon atoms in the skeletal structure may form regions composed of graphitized carbon.

[0024] The thin film 30 is a polyamic acid varnish which is a precursor solution obtained by dissolving a polyimide resin, which is a thermosetting resin, in an organic solvent. The polyamic acid varnish is directly applied using a coating device such as a bar coater or a spin coater so as to cover one end face portion 22a in the axial direction of the SiC substrate 22 constituting the rotary seal ring 20. After being imidized by drying and curing treatment, it is heat-cured at a temperature of 1200 °C or lower in an inert atmosphere, and further fired to form a vitreously carbonized skeleton. That is, the skeletal structure of carbon atoms in the thin film 30 is derived from polyamic acid.

[0025] In addition, when the thin film 30 is formed into a thin film with a thickness within a predetermined range, it is possible to prevent the film from tearing, and it is possible to vitreously carbonize the thermosetting resin by firing at a relatively low temperature. Furthermore, before initial use, the thin film 30 may be formed to have a thickness of 1 μm to 100 μm. If the film thickness is thinner than the above value, peeling will occur between the SiC substrate 22 and the film. If the film thickness is thicker than the above value, cracks will occur during film formation. Also, the optimum value of the film thickness of the thin film 30 may be set according to the particle size of the filler or additive dispersed in the film.

[0026] Also, the end face portion 22a of the SiC substrate 22 covered by the thin film 30 has an arithmetic mean roughness Ra on its surface of 0.1 μm or more, and the thin film 30 is formed in a state where a part of the thin film 30 enters into the fine recesses 22b of the end face portion 22a of the SiC substrate 22.

[0027] Also, the hardness of the thin film 30 and the SiC substrate 12 was tested with a nanoindenter, and it was confirmed that the SiC substrate 12 showed a harder value than the thin film 30.

[0028] As described above, the thin film 30 of this embodiment is mainly formed with a vitreous carbon region on the surface by firing a polyimide resin, which is a thermosetting resin, at a temperature of 1200 °C or lower. The composition of the film in the thin film 30 can be determined by analyzing the composition of the film by, for example, XRD, Raman spectroscopy, or thermal analysis.

[0029] Further, the thin film 30 is preferably formed by baking a polyimide resin, which is a thermosetting resin, at a temperature of 800°C to 1200°C or lower.

[0030] As shown in FIG. 3, in the thin film 30, granular high thermal conductivity fillers 40 and low friction fillers 41 having dimensions equal to or smaller than the film thickness of the thin film 30 are substantially uniformly dispersed. In FIG. 3, for convenience of explanation, the high thermal conductivity fillers 40 and the low friction fillers 41 are illustrated with the same particle size. Further, the fillers may be nanofillers.

[0031] In this embodiment, natural graphite, which has higher thermal conductivity than the glassy carbon constituting the thin film 30, is used as the high thermal conductivity filler 40. In addition to natural graphite, fillers such as artificial graphite and carbon black (C.B.) may be used as the high thermal conductivity filler 40.

[0032] Further, it is preferable that the content of the high thermal conductivity filler 40 in the thin film 30 is adjusted to 1 to 50% by weight.

[0033] In this embodiment, kaolin clay, which has a lower coefficient of friction than the glassy carbon constituting the thin film 30, is used as the low friction filler 41. In addition to kaolin clay, fillers such as natural graphite, artificial graphite, and molybdenum disulfide may be used as the low friction filler 41.

[0034] In the thin film 30 of this embodiment, by adding the high thermal conductivity filler 40 as the main filler, the thermal conductivity of the thin film 30 mainly composed of glassy carbon can be increased, and by adding a small amount of the low friction filler 41, the coefficient of friction on the surface of the thin film 30 can be reduced. In particular, by using kaolin clay as the low friction filler 41, the coefficient of friction in a dry environment can be reduced.

[0035] Further, it is preferable that the total content of the fillers contained in the thin film 30 is 75% by weight or less in order to exhibit the wear resistance of the glassy carbon.

[0036] Further, the thin film 30 may have the type, number, and content ratio of the filler contained in the film freely changed according to the characteristics required for the sliding surface 21. For example, by adding cerium oxide as a filler in addition to the above-described high thermal conductivity filler 40 and low friction filler 41, silicate deposits due to long-life coolant (LLC) can be removed. Further, by adding highly crystalline natural graphite, artificial graphite, or metal powder (or metal oxide) as a filler, electrical characteristics can be imparted to the thin film.

[0037] In addition, for the analysis of the graphitization degree of the surface of the thin film 30, a spectroscopic analyzer manufactured by Nanophoton was used, and the measurement was performed at a center frequency of 2082.24 cm -1 , an excitation wavelength of 532.36 nm, and a laser intensity of 0.8 mW. IG is the intensity of the G peak that appears at a center frequency of 1574 to 1576 cm -1 . ID is the intensity of the D peak that appears at a center frequency of 1344 to 1348 cm -1 . A plurality of points in a specific region of the sample were measured, and the intensity ratio ID / IG was calculated from the G and D peak intensities of the averaged spectrum. If the value is greater than 1, it represents the vitreous carbon in the present invention.

[0038] Next, regarding the rotating seal ring 20 on which the thin film 30 is formed, the results of a Ring-on-Ring friction and wear test performed under the following conditions will be described. Also, the stationary seal ring 10 is not formed with a thin film as described above, and at least the sliding surface 11 is formed of SiC.

[0039] Load = 10 N Surface pressure of the sliding surface of the stationary seal ring = 0.25 MPa Rotation speed of the rotating seal ring = 74 rpm PV value = 0.008 MPa·m / sec Test time = until the sliding distance reaches 1000 m Fluid to be sealed = atmosphere

[0040] The formation results of the thin film 30 of the rotary seal ring 20 (Samples F to M) and the test results of the Ring-on-Ring friction and wear test in this embodiment were as shown in Table 1. Note that for the Ring-on-Ring friction and wear test, in a lubrication-free environment, the determination of usability was made based on whether seizure occurred on the sliding surface. Furthermore, after the Ring-on-Ring friction and wear test, the presence or absence of peeling of the thin film 30 from the sliding surface 21 of the rotary seal ring 20 and the presence or absence of cracks were confirmed. Regarding the confirmation of the presence or absence of peeling of the thin film, deposits were removed by blowing air onto the sliding surface 21 of the rotary seal ring 20, and if the remaining area ratio of the thin film 30 in the fine recess 22b of the end face portion 22a was 80% or less at a magnification of 5 times with an optical microscope within the contact range, it was determined that there was peeling from the sliding surface 21 of the rotary seal ring 20. Regarding the confirmation of the presence or absence of cracks in the thin film, deposits were removed by blowing air onto the sliding surface 21 of the rotary seal ring 20, and the presence or absence of cracks was confirmed.

[0041]

Table 1

[0042] Regarding the thin film 30 of the rotary seal ring 20 that had no seizure on the sliding surface and no peeling or cracking of the thin film 30 from the sliding surface 21 of the rotary seal ring 20 in a lubrication-free environment, it was found that the thickness was 1 μm to 100 μm (Samples F, G, H, I, K).

[0043] Next, regarding the rotary seal ring 20 on which the thin film 30 was formed in this embodiment, the content ratio (weight %) of the high thermal conductivity filler 40 in the film was changed and prepared, and the results of the Ring-on-Ring friction and wear test under the following conditions will be described. Note that the thin film 30 of the rotary seal ring 20 is formed in a state where the thickness is unified to 20 μm. Also, the thin film 30 is formed in a state where the content ratio of the low friction filler 41 in the film is unified to 5 wt%. Also, the stationary seal ring 10 is not formed with a thin film as described above, and at least the sliding surface 11 is formed of SiC.

[0044] Load = 10 N Surface pressure of the sliding surface of the stationary seal ring = 0.25 MPa Rotation speed of the rotating seal ring = 74 rpm PV value = 0.008 MPa·m / sec Test time = until the sliding distance reaches 1000 m Fluid to be sealed = atmosphere

[0045] The test results of the Ring-on-Ring friction and wear test of the rotating seal ring 20 (samples N to S) in this example were as shown in Table 2. Note that for the Ring-on-Ring friction and wear test, in a lubrication-free environment, the judgment of usability was made based on whether seizure of the sliding surface occurred. Furthermore, after the Ring-on-Ring friction and wear test, in the same manner as in Table 1, the presence or absence of cracks in the thin film 30 of the sliding surface 21 of the rotating seal ring 20 was confirmed.

[0046]

Table 2

[0047] In a lubrication-free environment, for the thin film 30 of the rotating seal ring 20 that had no seizure of the sliding surface due to an increase in the friction coefficient accompanying the temperature rise of the sliding surface and had no cracks, it was found that the content rate of the high thermal conductivity filler 40 was 10% by weight or more, and the total content rate of the high thermal conductivity filler 40 and the low friction filler 41 was 30% by weight or less (samples O, P, Q, R).

[0048] When the stationary seal ring 10 on the mating side is formed of carbon, which is a soft material, with respect to the sliding surface 21 where the thin film 30 is not formed, foreign matter may enter between the sliding surfaces 11 and 21, causing the foreign matter to bite into the sliding surface 11 of the stationary seal ring 10 formed of soft carbon. As a result, the sliding surface 11 is scraped, resulting in surface roughness, loss of smoothness of the sliding surface, and an adverse effect on the friction coefficient. Thus, the sliding surfaces of sliding parts formed of carbon have a problem with foreign matter resistance. In contrast, in this embodiment, the rotating seal ring 20 is configured such that the hard SiC base material 22 is coated with the thin film 30, and the stationary seal ring 10 on the mating side is also formed of hard SiC. Therefore, with respect to the intrusion of foreign matter between the sliding surfaces 11 and 21, the graphite region, which is softer than the glassy carbon mainly constituting the thin film 30, is preferentially scraped, making it difficult for surface roughness of the SiC base materials 12 and 22 to occur, which would adversely affect the friction coefficient of the sliding surface.

[0049] As described above, since the SiC base material 22 of the rotating seal ring 20 according to the present invention is directly coated with the thin film 30 mainly composed of glassy carbon and containing the high thermal conductivity filler 40 and the low friction filler 41, the frictional heat generated by the relative sliding with the sliding surface 11 of the stationary seal ring 10 is directly transferred from the thin film 30 to the SiC base material 22. Therefore, the temperature rise of the sliding surface 21 can be suppressed. In addition, since the SiC base material 22 faces a fluid such as the fluid to be sealed, heat is not likely to remain due to heat dissipation or heat transfer to the seal cover 5 (see FIG. 1). Further, since the thin film 30 mainly consists of glassy carbon, it has excellent wear resistance and is difficult to bite even in a starved lubrication state.

[0050] Further, the thin film 30 may be prone to peeling when directly coated on the SiC substrate 22 mainly composed of vitreous carbon. However, since graphite is mixed in the thin film 30, a part of the graphite region enters the unevenness on the surface of the SiC substrate 22, so that the adhesion of the thin film 30 to the SiC substrate 22 can be enhanced. Further, when the graphite region of the thin film 30 constituting the sliding surface 21 is sheared between the graphite layers bonded by weak van der Waals forces due to friction with the sliding surface 11 of the stationary seal ring 10 (see the enlarged part in FIG. 4), and is pushed axially by the pressing force between the sliding surfaces 11 and 21, a part of the thin film 30 enters and remains in the fine recess 22b of the end face portion 22a of the SiC substrate 22, thereby smoothing the sliding surface 21 (see the enlarged part in FIG. 5). As a result, the thin film 30 remaining in the fine recess 22b can exhibit the self-lubricity of graphite with respect to the sliding surface 11 of the stationary seal ring 10, so that a stable low-friction effect can be obtained under a wide range of use conditions such as in a fluid lubrication region, a boundary lubrication region, and a non-lubricated environment. Although vitreous carbon also has self-lubricity, graphite is superior to vitreous carbon in self-lubricity.

[0051] In addition, the sliding surface 21 of the rotating seal ring 20 coated with the thin film 30 is added with the functions of the high thermal conductivity filler 40 and the low friction filler 41 having dimensions equal to or less than the film thickness of the thin film 30. Even for the thin film 30 with a thin film thickness, the high thermal conductivity filler 40 and the low friction filler 41 are difficult to fall off, and in particular, the high thermal conductivity filler 40 can be suppressed from protruding from the sliding surface 21. Therefore, it is difficult to damage the sliding surface 11 of the stationary seal ring 10 due to friction. Further, since the thin film 30 containing the filler is coated on the SiC substrate 22 by firing, a part of the filler enters the unevenness on the surface of the SiC substrate 22, so that the adhesion of the thin film 30 to the SiC substrate 22 can be enhanced.

[0052] Further, the thin film 30 includes a high thermal conductivity filler 40 having a higher thermal conductivity than the vitreous carbon constituting the thin film 30, thereby enhancing the thermal conductivity of the sliding surface 21 composed mainly of vitreous carbon. As a result, the frictional heat generated by the relative sliding with the sliding surface 11 of the stationary seal ring 10 is more likely to be further transferred from the thin film 30 to the SiC base material 22. Note that, by using a high thermal conductivity filler 40 that is softer than the sliding surface 11 of the stationary seal ring 10, it is difficult to damage the mating sliding surface 11 due to friction.

[0053] Also, the thin film 30 can enhance the lubricity of the sliding surface 21 by including a low friction filler 41 having a smaller friction coefficient than the vitreous carbon constituting the thin film 30.

[0054] Furthermore, since the thin film 30 is formed only on the sliding surface 21 of the rotary seal ring 20, the graphite shear block P30 (see the enlarged portion in FIG. 4) derived from the thin film 30 generated between the sliding surfaces 11 and 21 is pushed axially by the pressing force between the sliding surfaces 11 and 21, enters and adheres into the fine recess 12b of the end face portion 12a of the SiC base material 12 constituting the sliding surface 11 of the stationary seal ring 10, and forms an adhered film 31, thereby also smoothing the sliding surface 11 of the stationary seal ring 10 (see the enlarged portion in FIG. 5). As a result, in the sliding portion between the sliding surfaces 11 and 21, the ratio of the sliding portions of SiC and graphite, vitreous carbon and graphite, or graphite and graphite increases, so that a better low friction effect can be obtained.

[0055] In addition, the thin film 30 is formed by directly applying a polyamic acid varnish, which is a precursor solution obtained by dissolving a polyimide resin, which is a thermosetting resin, in an organic solvent, to the end face portion 22a of the SiC base material 22 and then baking it. Therefore, the thin film 30 has high adhesion to the SiC base material 22 by entering the fine recess 22b of the end face portion 22a of the SiC base material 22. Note that, by adjusting the viscosity of the polyamic acid varnish, which is a precursor solution of a polyimide resin with excellent film-forming properties, to an arbitrary viscosity, applying it, and forming a film, it can suitably contract in the plane direction and the thickness direction, and the adhesion can be improved. Therefore, there is no limitation on the film-forming area of the thin film 30.

[0056] In addition, the thin film 30 of the present invention can be created by thinly applying a polyamic acid varnish and firing it at a relatively low temperature of 800°C to 1200°C or lower. Therefore, peeling, tearing, etc. of the thin film 30 due to thermal shrinkage are less likely to occur, it has excellent processability, and can exhibit excellent wear resistance due to glassy carbon as the sliding surface 21. Further, the thin film 30 is formed to be thin with a thickness of 1 μm to 100 μm, and by including a filler having a dimension equal to or less than the film thickness of the thin film 30, the gas generated inside the thin film 30 during firing can easily escape, preventing the generation of cracks.

[0057] In addition, since the hardness of the thin film 30 is smaller than that of the sliding surface 11 of the stationary seal ring 10, that is, the hardness of the SiC base material 12, the thin film 30 becomes softer than the sliding surface 11 of the stationary seal ring 10, and it is difficult to damage the sliding surface 11 of the stationary seal ring 10 by friction. Furthermore, since the hardness of the thin film 30 is smaller than that of the SiC base material 22 of the rotating seal ring 20, when foreign matter enters between the sliding surfaces 11 and 21, the graphite region of the particularly soft thin film 30 is preferentially sheared, promoting the smoothing of the sliding surface 21, and the exposed hard SiC base material 22 end face portion 22a and glassy carbon region can enhance the foreign matter resistance. Therefore, the self-lubricity and foreign matter resistance of graphite can be achieved simultaneously between the sliding surfaces 11 and 21.

[0058] In addition, the base material of the rotating seal ring 20 is formed of SiC, which is a ceramic. Since the SiC base material 22 is porous, there are many fine recesses 22b into which a part of the thin film 30 enters the end face portion 22a, and the surface roughness is more likely to occur than that of metal. Therefore, the thin film 30 is likely to adhere to the base material surface. Further, since the arithmetic mean roughness Ra of the surface of the end face portion 22a of the SiC base material 22 on which the thin film 30 is formed is 0.1 μm or more, a part of the thin film 30 is more likely to enter the fine recesses 22b in the end face portion 22a. Therefore, even if the graphite region of the thin film 30 is sheared by friction with the sliding surface 11 of the stationary seal ring 10, a part of the thin film 30 is held in the fine recesses 22b and is difficult to fall off between the sliding surfaces 11 and 21.

[0059] In addition, the end face portion 22a of the SiC base material 22 is entirely covered by the thin film 30. In other words, since the surface of the base material is not exposed, a part of the thin film 30 enters into all the fine recesses 22b in the end face portion 22a. Therefore, the sliding surface 21 is easily smoothed by shearing the graphite region of the thin film 30.

[0060] Moreover, since the thickness of the thin film 30 is 1 μm to 100 μm, peeling of the thin film 30 from the end face portion 22a of the SiC base material 22 or cracking of the thin film 30 can be prevented. Therefore, it can be used as a film for a sliding component.

[0061] Furthermore, since the thickness of the thin film 30 is larger than the arithmetic mean roughness Ra on the surface of the end face portion 22a of the SiC base material 22, that is, the thickness of the thin film 30 is larger than the unevenness of the surface of the end face portion 22a of the SiC base material 22, a part of the thin film 30 easily enters into the fine recesses 22b of the SiC base material 22. Due to the friction between the sliding surface 11 of the stationary seal ring 10 and the thin film 30, the graphite region of the thin film 30 is surely sheared. Therefore, a part of the thin film 30 easily remains in the fine recesses 22b, and it is easy to exhibit a low friction effect.

[0062] In addition, since the base material and the sliding surface of the rotary seal ring 20 can be formed of different materials, while giving the base material the rigidity and high thermal conductivity of ceramics such as SiC, the thin film 30 on the sliding surface 21 can be given the self-lubricity and wear resistance of glassy carbon, the self-lubricity of graphite, and the functions of various fillers. Furthermore, by changing the base material to an inexpensive material, the cost of the sliding component can be reduced.

[0063] In addition, since the thin film 30 mainly consists of glassy carbon, it is highly hard and also excellent in wear resistance. In particular, in sliding in slurry, it is extremely excellent in resistance to foreign substances. Regarding the resistance to foreign substances of the thin film 30, seizure of the sliding surface does not occur due to high friction like sliding between SiCs even in a dry environment or under boundary lubrication.

[0064] As described above, the embodiments of the present invention have been described with reference to the drawings. However, the specific configuration is not limited to these embodiments, and even if there are changes or additions within the scope not departing from the gist of the present invention, they are included in the present invention.

[0065] For example, in the above embodiment, as the sliding part, a mechanical seal for general industrial machinery has been described as an example. However, other mechanical seals such as those for automobiles and water pumps may also be used. Further, it is not limited to mechanical seals, and sliding parts other than mechanical seals such as plain bearings may also be used. Furthermore, since the thin film 30 can also be formed on the inner peripheral surface of the bearing, it can also be applied to the sliding parts constituting a radial bearing or the like.

[0066] Also, in the above embodiment, the mechanical seal to which the sliding part is applied has been described as being used in a non-lubricated environment. However, it is not limited to this, and it may be used in a fluid lubrication region or a boundary lubrication region in which a liquid, which is a fluid to be sealed, is interposed between the sliding surfaces.

[0067] Also, in the above embodiment, an example in which the thin film 30 is provided only on the rotating seal ring 20 has been described. However, the thin film 30 may be provided only on the stationary seal ring 10, or may be provided on both the rotating seal ring 20 and the stationary seal ring 10.

[0068] Also, in the above embodiment, the thin film 30 has been described as being derived from a polyamic acid, which is a precursor solution obtained by dissolving a polyimide resin in an organic solvent. However, it is not limited to this, and the thin film may be derived from a precursor solution obtained by dissolving one or more thermosetting resins selected from phenolic resins, melamine resins, urea resins, epoxy resins, unsaturated polyester resins, silicone resins, diallyl phthalate resins, polyimide resins, polyurethane resins, etc. in an organic solvent.

[0069] Also, the filler is not limited to granular ones, and may be fibrous ones, for example.

[0070] Further, if the thin film 30 can obtain sufficient lubricity on the sliding surface 21 due to the self-lubricity of graphite, the low-friction filler 41 may not be included.

[0071] Also, in the above embodiment, the thin film 30 is described in terms of being glassy carbonized by changing the firing temperature in the range of 800°C to 1200°C or lower and firing for 30 minutes in a nitrogen atmosphere. However, it is not limited to this, and the firing temperature may be set to the same temperature in the range of 800°C to 1200°C or lower, and the firing time may be changed.

[0072] Also, the end face portion 22a of the SiC base material 22 coated with the thin film 30 may have an arithmetic mean roughness Ra on its surface of 0.1 μm or less depending on the film thickness of the thin film 30.

[0073] Also, in the above embodiment, the stationary seal ring 10 and the rotating seal ring 20 are described as being formed of SiC. However, it is not limited to this, and any sliding material that is used as a sliding material for mechanical seals is applicable. Note that as SiC, there may be a sintered body using boron, aluminum, carbon, etc. as a sintering aid, a material composed of two or more phases with different components and compositions, for example, SiC in which graphite particles are dispersed, reaction-sintered SiC composed of SiC and Si, etc. Also, in addition to the above sliding materials, other ceramics such as alumina, zirconia, silicon nitride (Si3N4), metal materials, resin materials, composite materials, etc. are also applicable.

Explanation of Reference Numerals

[0074] 10 Stationary seal ring (sliding part) 11 Sliding surface 12 SiC base material (base material) 12a End face portion 12b Fine recess 20 Rotating seal ring (sliding part) 21 Sliding surface 22 SiC base material (base material) 22a End face portion 22b Fine recess 30 Thin film 30a Surface 31 Transfer film 40 High thermal conductivity filler (filler) 41 Low friction filler (filler) P30 Shearing block

Claims

**Claim 1** A sliding component having sliding surfaces that slide relative to each other, wherein a thin film mainly composed of glassy carbon is directly coated on the base material of the sliding component, and the sliding surfaces are composed of the thin film, and the thin film contains a high thermal conductivity filler having a higher thermal conductivity than the glassy carbon constituting the thin film. A sliding component. **Claim 2** The sliding component according to claim 1, wherein the thin film mainly consists of glassy carbon and contains graphite. **Claim 3** The sliding component according to claim 1 or 2, wherein the thin film contains a filler having a dimension equal to or less than the film thickness of the thin film. **Claim 4** The sliding component according to any one of claims 1 to 3, wherein the thin film contains a low friction filler having a lower friction coefficient than the glassy carbon constituting the thin film.

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