JP2012067900A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing filled with fluorine grease having excellent seizure resistance, wear resistance and corrosion resistance to improve peeling resistance of a DLC (Diamond-Like Carbon) film formed on an inner/outer ring raceway surface, etc. and suppress a reaction between fluorine and steel by the DLC film.SOLUTION: The rolling bearing 1 includes an inner ring 2, an outer ring 3, a plurality of rolling elements 4 and a retainer 5 are provided. Fluorine grease 7 is filled around the rolling elements 4. Hard films 8 are deposited on the inner ring raceway surface 2a and the outer ring raceway surface 3a, etc to be curved surfaces. The hard film 8 comprises a base layer which is directly deposited on the surface and is mainly composed of Cr, a mixed layer which is deposited on the base layer and is mainly composed of WC and DLC, and a surface layer which is deposited on the mixed layer and is mainly composed of DLC. The mixed layer is constituted such that the content rate of WC is reduced continuously or stepwise, while the content rate of DLC is increased continuously or stepwise, from the base layer side to the surface layer side.

Description

  The present invention relates to a rolling bearing, and more particularly to a rolling bearing in which a hard film containing diamond-like carbon is formed on a raceway surface or a cage sliding contact surface when fluorine grease is sealed.

  The hard carbon film is a hard film generally called diamond-like carbon (hereinafter referred to as DLC. A film / layer mainly composed of DLC is also referred to as a DLC film / layer). In addition, hard carbon has various names such as hard amorphous carbon, amorphous carbon, hard amorphous carbon, i-carbon, diamond-like carbon, and these terms are not clearly distinguished.

  The essence of DLC in which such terms are used is structurally an intermediate structure of both diamond and graphite mixed. It is as hard as diamond and has excellent wear resistance, solid lubricity, thermal conductivity, chemical stability, and corrosion resistance. For this reason, for example, it is being used as a protective film for molds / tools, wear-resistant mechanical parts, abrasives, sliding members, magnetic / optical parts, and the like. As a method for forming such a DLC film, physical vapor deposition (hereinafter referred to as PVD) such as sputtering or ion plating, chemical vapor deposition (hereinafter referred to as CVD), unbalanced magnetron sputtering ( Hereinafter, a method such as UBMS) is employed.

  Conventionally, an attempt has been made to form a DLC film on a raceway surface of a bearing ring of a rolling bearing, a rolling surface of a rolling element, a cage sliding contact surface, and the like. DLC films generate extremely large internal stress during film formation, and have high hardness and Young's modulus, but their deformability is extremely small, so they have the disadvantages of poor adhesion to the substrate and easy peeling. ing. For this reason, when forming a DLC film on each said surface in a rolling bearing, it is necessary to improve adhesiveness.

  For example, assuming that the adhesion of the DLC film is improved by providing an intermediate layer, chromium (hereinafter referred to as Cr), tungsten (hereinafter referred to as W) is formed on the raceway groove formed of a steel material or the rolling surface of the rolling element. ), Titanium (hereinafter referred to as Ti), silicon (hereinafter referred to as Si), nickel, and an underlayer having a composition containing at least one element of iron, and the constituent elements and carbon of the underlayer And a diamond-like carbon layer comprising an intermediate layer that is larger than the base layer side on the opposite side of the base layer, and has a carbon content of 0.02% by mass to 5% by mass with argon and carbon. However, a rolling device formed in this order has been proposed (see Patent Document 1). Similarly, an intermediate layer is provided to improve adhesion, and a plurality of layers are formed on the cage surface of the rolling bearing, and a predetermined hardness is provided between the outermost layer layer and the cage. A cage with an intermediate layer interposed therebetween has been proposed (see Patent Document 2).

  Also, assuming that the adhesion of the DLC film is improved by the anchor effect, irregularities with a height of 10 to 100 nm and an average width of 300 nm or less are formed on the orbital surface by ion bombardment, and a DLC film is formed on the orbital surface. A rolling bearing has been proposed (see Patent Document 3).

  In addition, a hardened layer having undergone a predetermined treatment was formed on the surface of the cage base material, a hard film having a higher hardness was coated on the surface of the hardened layer, and a soft film having a solid lubricating effect was coated on the hard film surface. A cage, a manufacturing method thereof, and the like have been proposed (see Patent Document 4 and Patent Document 5).

  On the other hand, rolling bearings filled with fluorine grease are excellent in high temperature durability, and are therefore used as bearings used in automobile engine rooms and as toner fixing unit bearings for copying machines and printing machines. In addition, it is widely used in bearings for vacuum equipment because of its excellent vapor pressure characteristics. These fluorine greases exhibit good lubricity when a sufficient amount is present, but when the supply to the rolling contact part or the sliding part is insufficient and boundary lubrication occurs, perfluoro, which is the base oil, is used. Polyether (hereinafter referred to as PFPE) oil and steel (iron) as a bearing material react with each other to decompose the base oil and wear the steel, resulting in a short life. In addition, the PFPE oil itself is deteriorated and consumed by this reaction, so that the amount of lubricant that can be used is significantly reduced, and these may synergistically lead to a phenomenon that the bearing is burned out with a short life.

  As means for suppressing the reaction between the PFPE oil and the steel, an organic compound in which a film can be formed on the metal surface in fluorine grease has been proposed (see Patent Document 6). Moreover, it is thought that this reaction can be suppressed also by coating steel with hard films, such as the above-mentioned DLC film.

Japanese Patent No. 4178826 JP 2006-3000294 A Patent No. 3961739 Japanese Patent Laying-Open No. 2005-147306 JP 2005-147244 A Japanese Patent Laid-Open No. 2007-92012

  However, the raceway surfaces of the inner and outer rings that guide the rolling elements in the rolling bearing have a curved surface instead of a flat surface, and some have a shape in which the main curvature and the sub curvature are combined. The rolling surface of the rolling element is a circumferential surface in the case of cylindrical rollers and a spherical surface in the case of balls. The slidable contact surface of the cage is a surface that contacts the rolling element (a cage pocket surface) or a surface that contacts the raceway, and the shape thereof is a curved surface. When a DLC film is formed on the surface having the above-described shape, the residual stress in the film increases depending on the film structure and film formation conditions, and there is a possibility of peeling immediately after the film formation. Even if the film does not peel immediately after film formation, it may peel if subjected to a load such as rolling contact or a thermal shock due to local sliding heat generation when the bearing is used.

  When the DLC film is peeled off, metal contact occurs between the bearing members, and wear of the members causes wear powder to intervene on the rolling surface, leading to damage to the raceway surface. In the case of grease lubrication, grease degradation may be promoted by the catalytic action of the new metal surface. In particular, when fluorine grease is sealed, if the DLC film is peeled off, the problem due to the reaction between the PFPE oil and the steel becomes significant.

  The technology of each of the above patent documents is intended to prevent the peeling of the DLC film. However, in order to improve the practicality of the obtained rolling bearing, the film structure and film forming conditions for applying the DLC film are not limited. There is room for further improvement.

  The present invention has been made to cope with such a problem. In a rolling bearing in which fluorine grease is sealed, the peeling resistance of the DLC film formed on the inner and outer ring raceways is improved. An object of the present invention is to provide a rolling bearing capable of suppressing the reaction between fluorine and steel and having excellent seizure resistance, wear resistance, and corrosion resistance.

  The rolling bearing of the present invention includes an inner ring having an inner ring raceway surface on the outer periphery, an outer ring having an outer ring raceway surface on the inner periphery, a plurality of rolling elements that roll between the inner ring raceway surface and the outer ring raceway surface, A rolling bearing comprising fluorine grease sealed around the rolling element, wherein the rolling element is at least one selected from the inner ring, the outer ring, the rolling element, and the cage. One bearing member is made of an iron-based material, and is a curved surface of the bearing member made of the iron-based material, and the inner ring raceway surface, the outer ring raceway surface, the rolling surface of the rolling element, and a slide of the cage A hard film is formed on at least one curved surface selected from the contact surfaces, and the hard film is formed on a ground layer mainly composed of Cr and directly formed on the curved surface. Tungsten carbide film (hereinafter referred to as WC) And a surface layer mainly composed of DLC formed on the mixed layer. The mixed layer is formed from the base layer side from the base layer side. The layer is characterized in that the content of WC in the mixed layer decreases and the content of DLC in the mixed layer increases in a continuous or stepwise manner toward the surface layer side.

  The rolling element is a ball, and the inner ring raceway surface and the outer ring raceway surface are circular curved surfaces that guide the rolling element.

  The fluorine grease is a grease containing PFPE oil as a base oil and fluorine resin powder as a thickener.

  The surface layer has an inclined layer portion whose hardness increases continuously or stepwise from the mixed layer side on the side adjacent to the mixed layer.

  The surface layer is a layer formed using a UBMS apparatus using argon (hereinafter referred to as Ar) gas as a sputtering gas, and a graphite target and a hydrocarbon-based gas are used in combination as a carbon supply source. The ratio of the introduction amount of the hydrocarbon-based gas to the introduction amount 100 of Ar gas into the device is 1 to 5, the degree of vacuum in the device is 0.2 to 0.8 Pa, and becomes a substrate. The film is formed by depositing carbon atoms generated from the carbon supply source on the mixed layer under the condition that the bias voltage applied to the bearing member is 70 to 150V. Further, the hydrocarbon gas is methane gas.

  The bias potential for the bearing member serving as the base material is applied so as to be negative with respect to the ground potential. For example, the bias voltage of 150 V is that the bias potential of the base material is −150 V relative to the ground potential. Indicates that

  The inclined layer portion of the surface layer is formed by increasing a bias voltage applied to a bearing member serving as a base material continuously or stepwise.

  The underlayer and the mixed layer are layers formed using a UBMS apparatus using Ar gas as a sputtering gas, and the mixed layer is formed on a graphite target serving as a carbon supply source continuously or stepwise. The film is formed while increasing the sputtering power applied and decreasing the sputtering power applied to the WC target.

The hard film is brought into contact with SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 by applying a load with a maximum contact surface pressure of 0.5 GPa of Hertz. The specific wear amount of the hard film is less than 200 × 10 ⁻¹⁰ mm ³ / (N · m) when the counterpart material is rotated for 30 minutes at a rotational speed of 05 m / s. The hard film is characterized in that the sum of the average value of the indentation hardness and the standard deviation value is 25 to 45 GPa. The hard film has a critical peel load in a scratch test of 50 N or more.

  The hard film has a thickness of 0.5 to 3 μm, and the ratio of the thickness of the surface layer to the thickness of the hard film is 0.8 or less.

  The iron-based material is selected from high carbon chromium bearing steel, carbon steel, tool steel, and martensitic stainless steel. Further, the surface on which the hard film is formed has a Vickers hardness of Hv650 or more.

  The iron-based materials forming the inner ring, the outer ring, and the rolling elements are high carbon chromium bearing steel, carbon steel, tool steel, or martensitic stainless steel, respectively. In the inner ring, the outer ring, or the rolling element, the hardness of the curved surface on which the hard film is formed is Hv 650 or more in terms of Vickers hardness.

  The iron-based material forming the cage is a cold rolled steel plate, carbon steel, chromium steel, chromium molybdenum steel, nickel chromium molybdenum steel, or austenitic stainless steel. In the cage, the hardness of the curved surface on which the hard film is formed is Vvker hardness of Hv450 or more.

  In the curved surface on which the hard film is formed, a nitride layer is formed by nitriding before the hard film is formed. In particular, the nitriding treatment is a plasma nitriding treatment. Further, the hardness of the curved surface after the nitriding treatment is characterized in that the Vickers hardness is Hv1000 or more.

  In the inner ring, the outer ring, or the rolling element, a surface roughness Ra of a curved surface on which the hard film is formed is 0.05 μm or less. In the cage, the curved surface on which the hard film is formed has a surface roughness Ra of 0.5 μm or less.

  The rolling bearing of the present invention is formed by forming a hard film having a predetermined film structure including DLC on a curved surface of a bearing member made of an iron-based material. The underlayer made of Cr formed directly on each curved surface has good compatibility with the iron-based material, and has better adhesion than W or Si. In addition, WC used for the mixed layer has intermediate hardness and elastic modulus between Cr and DLC, and concentration of residual stress after film formation hardly occurs. Further, the mixed layer of WC and DLC has a gradient composition, so that WC and DLC are physically coupled.

  With the above structure, the hard film has excellent peeling resistance while being formed on the curved inner and outer ring raceway surfaces, the rolling surface of the rolling element, and the sliding contact surface of the cage. As a result, the reaction between fluorine and steel is suppressed by the hard film, decomposition of the base oil and wear of the steel can be prevented, heat resistance and lubricity inherent in the fluorinated oil can be utilized, and a long life can be achieved. In addition, because it has excellent peeling resistance, it can exhibit the original characteristics of DLC, has excellent seizure resistance, wear resistance, and corrosion resistance, and damages such as the raceway surface and cage sliding surface even under severe lubrication conditions. Long life.

It is sectional drawing which shows an example of the rolling bearing of this invention. It is sectional drawing which shows the other example of the rolling bearing of this invention. It is sectional drawing which shows the other example of the rolling bearing of this invention. It is an enlarged view of the holder | retainer of FIG. It is a schematic cross section which shows the structure of a hard film. It is a schematic diagram which shows the film-forming principle of UBMS method. It is a schematic diagram of the UBMS apparatus provided with the AIP function. It is a figure which shows a friction tester. It is a figure which shows the testing machine used for the bearing life test.

  A hard film such as a DLC film has a residual stress in the film, and the residual stress varies greatly depending on the film structure, film forming conditions, and substrate shape. As a result of repeated experiments, it was found that the influence of the substrate shape was unexpectedly large. For example, on a flat surface, a hard film that does not peel immediately after film formation and has a large critical peel load in a scratch test may peel off immediately after film formation on curved surfaces such as inner and outer ring raceways and cage pocket surfaces of rolling bearings. Even if it does not peel off immediately after film formation, it may be easily peeled off during use. As a result of intensive studies, the present inventors have determined that a hard film formed on the inner and outer ring raceway surfaces of the rolling bearing, which is a curved surface, the rolling surface of the rolling element, and the cage sliding surface (pocket surface, etc.) (Cr), mixed layer (WC / DLC slope), and surface layer (DLC) are limited to a predetermined structure, so that the peel resistance can be greatly improved. It has been found that peeling of the film can be prevented.

  In the rolling bearing of the present invention, at least one bearing member selected from an inner ring, an outer ring, a rolling element, and a cage is made of an iron-based material, and fluorine grease is enclosed. The location where the hard film is formed is (1) the curved surface (surface) of the bearing member made of an iron-based material, among which (2) the inner ring raceway surface, the outer ring raceway surface, the rolling surface of the rolling element, and It is at least one curved surface selected from the sliding contact surface of the cage. The hard film is formed on a curved surface where members made of an iron-based material come into contact with each other.

  The fluorine grease sealed in the rolling bearing of the present invention is a grease using a fluorine-based oil such as PFPE oil as a base oil and a fluorine resin particle as a thickener. As the PFPE oil, any compound in which a hydrogen atom of an aliphatic hydrocarbon polyether is substituted with a fluorine atom can be used. In particular, those in which hydrogen atoms are completely substituted with fluorine atoms are preferable because of excellent heat resistance and oxidation deterioration resistance. Moreover, as said PFPE oil, what has a linear form and a side chain can be used. The fluorinated oil used as the base oil can be used alone or in combination of two or more. Further, as the base oil, a fluorinated oil and an oil other than the fluorinated oil may be mixed and used, or a fluorinated grease and other grease (such as urea grease) may be mixed and used.

  Fluorine resin particles used as a thickener for fluorine grease can be used as a powder having high affinity with fluorine-based oils such as the above-mentioned PFPE oil and having high temperature stability and chemical resistance. Examples of the fluororesin include perfluoro fluororesins such as polytetrafluoroethylene (PTFE) resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Can be mentioned. Among these, PTFE resin is preferable because it is excellent in high temperature stability and chemical resistance. These thickeners can be used alone or in combination of two or more.

  The base grease composition of the fluorine grease is preferably 50 to 90% by weight of fluorine-based oil and 50 to 10% by weight of fluororesin particles. By setting it as this range, it is possible to adjust to a preferred consistency that can reduce the torque for a long time with less leakage as the grease contained in the bearing.

  The fluorine grease can contain known additives as necessary. Examples of additives include antioxidants such as organic zinc compounds and amine compounds, metal deactivators such as benzotriazole, viscosity index improvers such as polymethacrylate and polystyrene, solid lubricants such as molybdenum disulfide and graphite, Examples thereof include rust preventives such as metal sulfonates and polyalcohol esters, friction reducing agents such as organic molybdenum, oily agents such as esters and alcohols, and antiwear agents such as phosphorus compounds. These may be added alone or in combination of two or more.

  The rolling bearing of this invention is demonstrated based on FIGS. FIG. 1 is a sectional view of a rolling bearing (deep groove ball bearing) having a hard film described later formed on the inner and outer ring raceway surfaces, and FIG. 2 is a rolling bearing (deep groove ball bearing) having a hard film formed on the rolling surface of the rolling element. 3 is a sectional view of a rolling bearing (deep groove ball bearing) in which a hard film is formed on the pocket surface of the cage, and FIG. 4 is an enlarged view of the cage of FIG.

  The rolling bearing 1 includes an inner ring 2 having an inner ring raceway surface 2a on the outer periphery, an outer ring 3 having an outer ring raceway surface 3a on the inner periphery, and a plurality of rolling elements that roll between the inner ring raceway surface 2a and the outer ring raceway surface 3a. 4 and a cage 5 that holds the rolling elements 4 at regular intervals. The axially opposite end openings of the inner and outer rings are sealed by the seal member 6, and the above-mentioned fluorine grease 7 is sealed in the bearing space. The grease 7 is sealed at least around the rolling element 4.

  In the rolling bearing of FIG. 1 (a), a hard film 8 is formed on the outer peripheral surface (including the inner ring raceway surface 2a) of the inner ring 2, and in the rolling bearing of FIG. 1 (b), the inner peripheral surface ( A hard film 8 is formed on the outer ring raceway surface 3a). When the hard film 8 is formed on the inner / outer rings, it may be formed at least on the raceway surface. Therefore, as shown in each figure, it may be formed on the entire inner ring outer peripheral surface, the outer ring outer peripheral surface, or the entire inner / outer ring.

  In the rolling bearing of FIG. 2, a hard film 8 is formed on the rolling surface of the rolling element 4. Since the rolling bearing of FIG. 2 is a deep groove ball bearing, the rolling element 4 is a ball, and its rolling surface is the entire spherical surface. When a cylindrical roller bearing or a tapered roller bearing is used as a rolling bearing other than that shown in the figure, when the hard film 8 is formed on the rolling element, it is formed at least on the rolling surface (such as the outer circumference of the cylinder). I just need it.

  As shown in FIGS. 1 and 2, the inner ring raceway surface 2 a of the deep groove ball bearing is a circular curved surface having an arc-shaped cross section in the axial direction in order to guide the balls as the rolling elements 4. Similarly, the outer ring raceway surface 3a is also a circular curved surface having an arc-shaped cross section in the axial direction. The radius of curvature of the arc groove is generally about 0.51 to 0.54 dw when the steel ball diameter is dw. In the case of using a cylindrical roller bearing or a tapered roller bearing as a rolling bearing other than the mode shown in the figure, the inner ring raceway surface and the outer ring raceway surface are curved at least in the circumferential direction in order to guide the rollers of these bearings. It becomes. In addition, in the case of a self-aligning roller bearing or the like, since a cylindrical roller is used as a rolling element, the inner ring raceway surface and the outer ring raceway surface are curved in the axial direction in addition to the circumferential direction. In the rolling bearing of the present invention, the inner ring raceway surface and the outer ring raceway surface may have any of the above shapes.

  In the rolling bearing of FIG. 3, a hard film 8 is formed on the sliding contact surface of the cage 5. As shown in FIG. 4, this cage 5 is a corrugated iron plate cage, and is a ball that is a rolling element 4 manufactured by combining two members 5 a and 5 a that are press-molded using an iron-based material described later. A cage pocket 5b is formed to hold the. An inner peripheral surface (pocket surface) of the cage pocket 5b is a sliding contact surface with the rolling element 4, and a hard film 8 is formed on the pocket surface. The hard film 8 may be formed on at least one sliding contact surface selected from the sliding contact surface with the raceway (inner ring 2 or outer ring 3) and the sliding contact surface with the rolling element 4. In addition to the sliding contact surface of the cage 5, a hard film is also formed on the inner ring raceway surface 2a, the outer ring raceway surface 3a, and the rolling surface of the rolling element 4 shown in FIGS. Also good.

  As the iron-based material constituting the inner ring 2, the outer ring 3, and the rolling element 4 to be formed with the hard film 8, any steel material generally used as a bearing member can be used. For example, high carbon chromium bearing steel, carbon steel, tool steel, martensitic stainless steel and the like can be mentioned. In these bearing members (the inner ring 2, the outer ring 3, and the rolling element 4), it is preferable that the hardness of the curved surface on which the hard film is formed is Hv650 or more in terms of Vickers hardness. By setting it as Hv650 or more, a hardness difference with a hard film | membrane (underlayer) can be decreased and adhesiveness can be improved.

  In the inner ring 2, the outer ring 3, or the rolling element 4, the surface roughness Ra of the curved surface on which the hard film 8 is formed is preferably 0.05 μm or less. When the surface roughness Ra exceeds 0.05 μm, it is difficult to form a hard film at the tip of the projection having the roughness, and the film thickness is locally reduced.

  As the iron-based material constituting the cage 5 that is the target for forming the hard film 8, any material generally used as a cage material can be used. For example, cold rolled steel sheet, carbon steel, chromium steel, chromium molybdenum steel, nickel chromium molybdenum steel, austenitic stainless steel, and the like can be given. In this cage 5, the hardness of the sliding contact surface (curved surface) on which the hard film 8 is formed is preferably Hv450 or higher in terms of Vickers hardness. By setting it as Hv450 or more, the hardness difference with a hard film | membrane (underlayer) can be reduced as much as possible, and adhesiveness can be improved.

  In the cage 5, the surface roughness Ra of the slidable contact surface (curved surface) on which the hard film 8 is formed is preferably 0.5 μm or less. When the surface roughness Ra exceeds 0.5 μm, the hard film formed at the tip of the projection having the roughness is easily peeled off due to local stress concentration during sliding. Further, since the dirt is not easily removed, the hard film formed on the dirt may be easily peeled off.

  On the curved surface on which the hard film 8 of each member is formed, it is preferable that a nitride layer is formed by nitriding before the hard film is formed. As the nitriding treatment, it is preferable to perform a plasma nitriding treatment in which an oxide layer that hinders adhesion is hardly generated on the surface of the base material. Moreover, it is preferable that the hardness of the curved surface (surface) after nitriding is Hv 1000 or more in terms of Vickers hardness in order to further improve the adhesion with the hard film (underlayer).

  The structure of the hard film in the present invention will be described with reference to FIG. FIG. 5 is a schematic cross-sectional view showing the structure of the hard film 8 in the case of FIG. As shown in FIG. 5, the hard film 8 includes (1) an underlayer 8a mainly composed of Cr directly formed on the inner ring raceway surface 2a of the inner ring 2, and (2) an underlayer 8a. It has a three-layer structure including a mixed layer 8b mainly composed of WC and DLC and (3) a surface layer 8c mainly composed of DLC formed on the mixed layer 8b. Here, in the mixed layer 8b, the content of WC in the mixed layer decreases continuously or stepwise from the base layer 8a side to the surface layer 8c side, and the DLC content in the mixed layer This is a layer with a higher rate.

  Since the base layer 8a is a layer mainly composed of Cr, it has good compatibility with a bearing member made of an iron-based material as a base material, and adheres more closely to the base material than when W, Ti, Si, or the like is used. Excellent in properties. In particular, it has excellent adhesion to high carbon chromium bearing steel used as a bearing race material.

  The WC used for the mixed layer 8b has intermediate hardness and elastic modulus between Cr and DLC, and concentration of residual stress after film formation hardly occurs. When the mixed layer is a layer mainly composed of Cr and DLC in accordance with the base layer, sufficient adhesion cannot be obtained when the bearing is used. Thus, in the case where a hard film containing DLC having excellent peeling resistance is to be formed on the inner and outer ring raceway surfaces of the rolling bearing that is a curved surface or the rolling surface of the rolling element, the intermediate layer (mixed layer 8b) Material selection is also an important factor.

  In addition, since the mixed layer 8b has a gradient composition in which the content of WC is small toward the surface layer 8c side and the content of DLC is high, adhesion between both the base layer 8a and the surface layer 8c is improved. Excellent. In particular, in the mixed layer, WC and DLC are physically bonded, and the DLC content is increased on the surface layer 8c side, so that the adhesion between the surface layer 8c and the mixed layer 8b is excellent.

The surface layer 8c is a film mainly composed of DLC. The surface layer 8c preferably has an inclined layer portion 8d whose hardness increases continuously or stepwise from the mixed layer 8b side on the side adjacent to the mixed layer 8b. This is a portion obtained by changing (raising) the bias voltage continuously or stepwise in order to avoid a sudden change in the bias voltage when the bias voltage is different between the mixed layer 8b and the surface layer 8c. The inclined layer portion 8d changes the bias voltage as described above, and as a result, the hardness is inclined as described above. The reason why the hardness increases continuously or stepwise is that the composition ratio between the graphite structure (sp ² ) and the diamond structure (sp ³ ) in the DLC structure is biased toward the latter as the bias voltage increases. Thereby, there is no sudden hardness difference between the mixed layer and the surface layer, and the adhesion between the mixed layer 8b and the surface layer 8c is further improved.

  The thickness of the hard film 8 (total of the three layers) is preferably 0.5 to 3.0 μm. If the film thickness is less than 0.5 μm, the abrasion resistance and mechanical strength may be inferior, and if it exceeds 3.0 μm, the film is easily peeled off. Furthermore, the ratio of the thickness of the surface layer 8c to the thickness of the hard film 8 is preferably 0.8 or less. If this ratio exceeds 0.8, the gradient structure for physical bonding of WC and DLC in the mixed layer 8b becomes a discontinuous structure, so that the adhesiveness is likely to deteriorate.

  By making the hard film 8 into a three-layer structure of the base layer 8a, the mixed layer 8b, and the surface layer 8c having the above composition, the peel resistance is excellent.

The physical properties of the hard film 8 are SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780, and a contact with a load of 0.5 GPa maximum contact surface pressure of Hertz. The specific wear amount of the hard film is preferably less than 200 × 10 ⁻¹⁰ mm ³ / (N · m) when the counterpart material is rotated for 30 minutes at a rotational speed of 0.05 m / s. The form of this friction and wear test is an adhesive wear form close to the wear form in the bearing because the surface roughness of the counterpart material is small, and the specific wear amount is 200 × 10 ⁻¹⁰ mm ³ / (N · m) in the test. If it is less than (), it is effective in reducing wear even for local slip occurring on the raceway surface and the cage sliding surface.

  Moreover, it is preferable that the sum total of the average value of indentation hardness and a standard deviation value is 25-45 GPa. Within this range, a high effect is exhibited even in abrasive wear that occurs when a hard foreign object intervenes in the raceway surface or the cage sliding surface.

  Moreover, it is preferable that the critical peeling load in a scratch test is 50 N or more. The method for measuring the critical peel load in the scratch test is as shown in the examples described later. When the critical peel load is less than 50 N, the hard film is likely to peel when the bearing is used under high load conditions. Even if the critical peeling load is 50 N or more, the film may be easily peeled off depending on the case unless it is a film structure as in the present invention.

  In the rolling bearing of the present invention, by forming a hard film having the structure and physical properties as described above, even when subjected to a load such as rolling contact or a thermal shock due to local sliding heat generation when the bearing is used. In addition, the film can be prevented from being worn or peeled off, and even under severe lubrication, the track surface and the like are not damaged and the service life is extended. In addition, when the new metal surface is exposed due to damage to the raceway, etc., grease degradation is promoted by catalysis, but this hard film can prevent damage to the raceway surface and rolling surface due to metal contact. Can be prevented. In particular, the rolling bearing of the present invention is used by enclosing fluorine grease, but the hard film suppresses the reaction between fluorine and steel, and can prevent decomposition of the base oil and wear of the steel. The heat resistance and lubricity inherent in fluorinated oils can be utilized, and long life is achieved even in high-temperature applications. As a result, the rolling bearing of the present invention is suitable for use in high temperature environments, vacuum environments, and the like. Bearings used in automobile engine rooms, bearings for toner fixing parts such as copying machines and printing machines, bearings for vacuum equipment It can utilize suitably as.

  Hereinafter, a method for forming the hard film will be described. The hard film is obtained by forming the base layer 8a, the mixed layer 8b, and the surface layer 8c in this order on the film formation surface of the bearing member.

  The underlayer 8a and the mixed layer 8b are preferably formed using a UBMS apparatus using Ar gas as a sputtering gas. The film forming principle of the UBMS method using the UBMS apparatus will be described with reference to the schematic diagram shown in FIG. In the figure, the substrate 12 is a bearing member to be deposited, but is schematically shown as a flat plate. As shown in FIG. 6, an inner magnet 14 a and an outer magnet 14 b having different magnetic characteristics are arranged in the central portion and the peripheral portion of the round target 15, and the magnet 14 a is formed while forming a high-density plasma 19 near the target 15. , 14 b, a part 16 a of the magnetic force lines 16 reaches the vicinity of the base material 12 connected to the bias power source 11. The Ar plasma generated during the sputtering along the magnetic force lines 16a can be diffused to the vicinity of the base material 12. In such a UBMS method, an ion assist effect that causes Ar ions 17 and electrons to reach the base material 12 in a larger amount than the ordinary sputtering along the magnetic field lines 16a reaching the vicinity of the base material 12 due to the ion assist effect. A dense film (layer) 13 can be formed.

  As the target 15, a Cr target is used when forming the base layer 8a, and a WC target and a graphite target are used together when forming the mixed layer 8b. The target used for each layer is sequentially replaced every time the layers are formed.

  The mixed layer 8b is formed in a continuous or stepwise manner while increasing the sputtering power applied to the graphite target serving as the carbon supply source and decreasing the power applied to the WC target. Thereby, it can be set as the layer of the gradient composition which the content rate of WC becomes small toward the surface layer 8c side, and the content rate of DLC becomes high.

  The formation of the surface layer 8c is also preferably performed using a UBMS apparatus using Ar gas as the sputtering gas. More specifically, the surface layer 8c uses this apparatus, uses a graphite target and a hydrocarbon gas in combination as a carbon supply source, and the hydrocarbon system with respect to the introduction amount 100 of the Ar gas into the apparatus. Under the conditions where the ratio of the amount of gas introduced is 1 to 5, the degree of vacuum in the apparatus is 0.2 to 0.8 Pa, and the bias voltage applied to the bearing member as the base material is 70 to 150 V, The carbon atoms generated from the carbon supply source are preferably deposited on the mixed layer 8b. This preferable condition will be described below.

  Adhesiveness with the mixed layer 8b can be improved by using a graphite target and a hydrocarbon-based gas in combination as a carbon supply source. As the hydrocarbon-based gas, methane gas, acetylene gas, benzene and the like can be used, and are not particularly limited. However, methane gas is preferable from the viewpoint of cost and handleability.

  By setting the ratio of the introduction amount of the hydrocarbon-based gas to 1 to 5 (volume part) with respect to 100 introduction (volume part) of Ar gas into the UBMS apparatus (in the film formation chamber), the surface layer The adhesion with the mixed layer 8b can be improved without deteriorating the wear resistance of 8c.

  The degree of vacuum in the UBMS apparatus (inside the film forming chamber) is preferably 0.2 to 0.8 Pa as described above. More preferably, it is 0.25 to 0.8 Pa. When the degree of vacuum is less than 0.2 Pa, Ar plasma is not generated and film formation may not be possible. On the other hand, if the degree of vacuum is higher than 0.8 Pa, the reverse sputtering phenomenon tends to occur and the wear resistance may be deteriorated.

  The bias voltage applied to the bearing member as the base material is preferably 70 to 150 V as described above. More preferably, it is 100-150V. When the bias voltage is less than 70V, densification does not proceed and the wear resistance is extremely deteriorated, which is not preferable. On the other hand, when the bias voltage exceeds 150 V, reverse sputtering tends to occur, and the wear resistance may be deteriorated. On the other hand, if the bias voltage is too high, the surface layer becomes too hard and may be easily peeled off when the bearing is used.

  Moreover, it is preferable that the introduction amount of Ar gas which is sputtering gas is 40-150 ml / min. More preferably, it is 50-150 ml / min. When the Ar gas flow rate is less than 40 ml / min, Ar plasma is not generated and film formation may not be possible. On the other hand, if the Ar gas flow rate is higher than 150 ml / min, the reverse sputtering phenomenon tends to occur, so that the wear resistance may be deteriorated. When the amount of Ar gas introduced is large, the collision probability between Ar atoms and carbon atoms increases in the film forming chamber. As a result, the number of Ar atoms reaching the film surface is reduced, the effect of compacting the film by Ar atoms is reduced, and the wear resistance of the film is deteriorated.

  As described above, the inclined layer portion 8d of the surface layer 8c is obtained by forming the film while continuously or stepwise increasing the bias voltage applied to the bearing member that is the base material.

  As a hard film formed on the rolling bearing of the present invention, a hard film was formed on a predetermined base material, and the physical properties of the hard film were evaluated. A similar hard film was actually formed on the inner ring, outer ring, and cage pocket surface of the rolling bearing, and the bearing was evaluated. These will be described below as examples, comparative examples, and reference examples.

The formation conditions of the base material, UBMS apparatus, sputtering gas, underlayer and mixed layer used for evaluation of the hard film are as follows.
(1) Base material: Base material of inner ring and outer ring of each table (2) Base material dimension: Disk (φ48mm × φ8mm × 7mm: film formation on a plane)
(3) UBMS device: manufactured by Kobe Steel; UBMS202 / AIP composite device (4) Sputtering gas: Ar gas (5) Formation conditions of underlayer and mixed layer Underlayer: about 5 × 10 ⁻³ Pa in the film formation chamber The substrate was baked with a heater, the substrate was baked with a heater, the substrate surface was etched with Ar plasma, and a Cr layer was formed using a Cr target by the UBMS method. In addition, when using it as base layers other than Cr, it formed on the same conditions except using a corresponding target.
Mixed layer: The inside of the film forming chamber is evacuated to about 5 × 10 ⁻³ Pa, the substrate is baked with a heater, the substrate surface (or the Cr layer surface) is etched with Ar plasma, and then the WC target and The sputtering power applied to the graphite target was adjusted to incline the composition ratio of WC and DLC. In addition, when it was set as the mixed layer other than WC, it formed on the same conditions except using a corresponding target. (6) The conditions for forming the surface layer are shown in each table.

  An outline of the UBMS 202 / AIP combined apparatus is shown in FIG. FIG. 7 is a schematic diagram of a UBMS apparatus having an arc ion plating (hereinafter referred to as AIP) function. As shown in FIG. 7, the UBMS 202 / AIP combined device instantaneously vaporizes and ionizes the AIP evaporation source material 21 using the vacuum arc discharge to the base material 23 arranged on the disk 22, This is deposited on the base material 23 to increase the plasma density in the vicinity of the base material 23 and increase the ion assist effect by the non-equilibrium magnetic field of the sputtering evaporation source material (target) 24. (See FIG. 6), this is an apparatus having a UBMS function capable of controlling the characteristics of a film deposited on a substrate. By this apparatus, a composite film in which an AIP film and a plurality of UBMS films (including a composition gradient) are arbitrarily combined can be formed on a substrate. In this embodiment, a base layer, a mixed layer, and a surface layer are formed as a UBMS film on a bearing member as a base material.

Examples 1-9, 11, 12, Comparative Examples 2-6, Reference Examples 1-8
The inner ring and outer ring base materials shown in each table were ultrasonically cleaned with acetone and then dried. After drying, the substrate was attached to a UBMS / AIP composite apparatus, and an underlayer and a mixed layer of the materials shown in each table were formed under the above-described formation conditions. On top of that, a DLC film as a surface layer was formed under the film forming conditions shown in each table to obtain a test piece having a hard film. Note that “degree of vacuum” in each table is the degree of vacuum in the film forming chamber in the above apparatus. The obtained test piece was subjected to the following abrasion test, hardness test, film thickness test, and scratch test. The results are shown in each table.

Example 10
Manufactured by JEOL Ltd .: A substrate (Vickers hardness Hv1000) subjected to plasma nitrogen treatment using a radical nitriding apparatus was ultrasonically cleaned with acetone and then dried. After drying, the base material was attached to a UBMS / AIP composite apparatus, and an underlayer (Cr) and a mixed layer (WC / DLC) having the materials shown in Table 1 were formed under the above-described formation conditions. A DLC film, which is a surface layer, was formed on the film formation conditions shown in Table 1 to obtain a test piece having a hard film. About the obtained test piece, it uses for the test similar to Example 1, and the result is written together in Table 1. FIG.

<Friction test>
The obtained test piece was subjected to a friction test using a friction tester shown in FIG. FIG. 8A shows a front view, and FIG. 8B shows a side view. SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 is attached to the rotating shaft as a mating member 32, the test piece 31 is fixed to the arm portion 33, and a predetermined load 34 is applied to the upper part of the drawing. And a lubricant is interposed between the test piece 31 and the mating member 32 for 30 minutes at a rotation speed of 0.05 m / s under a maximum contact surface pressure of 0.5 GPa at room temperature (25 ° C.). Instead, the load cell 35 detected the frictional force generated between the counterpart material 32 and the test piece 31 when the counterpart material 32 was rotated. From this, the specific wear amount was calculated.

<Hardness test>
The indentation hardness of the obtained test piece was measured using a nanoindenter (G200) manufactured by Agilent Technologies. In addition, the measured value has shown the average value of the depth (location where hardness is stabilized) which is not influenced by surface roughness, and is measuring 10 each test piece.

<Film thickness test>
The film thickness of the hard film of the obtained test piece was measured using a surface shape / surface roughness measuring instrument (Taylor Hobson Co., Ltd .: Foam Talisurf PGI830). The film thickness was obtained by masking a part of the film forming portion and determining the level difference between the non-film forming portion and the film forming portion.

<Scratch test>
The obtained test piece was subjected to a scratch test using Nanotech: Level Test RST, and the critical peel load was measured. Specifically, the obtained test piece was tested with a diamond indenter with a tip radius of 200 μm at a scratch speed of 10 mm / min and a load load speed of 10 N / mm (continuously increasing the load), and judged on the testing machine screen. Then, the load at which the area of the exposed base material reached 50% with respect to the frictional trace on the screen (length in the friction direction 375 μm, width about 100 μm) was measured as the critical peel load.

<Film test on bearing member>
Film formation sites (inner ring, outer ring, and pocket surface of cage (two-split iron plate cage)) shown in each table of 6204 rolling bearing (deep groove ball bearing) under each condition of Example, Comparative Example, and Reference Example Actually, film formation was performed, and peeling of the hard film was confirmed immediately after film formation. In each example, the inner ring, the outer ring, and the cage have the same film forming conditions other than the base material. For each of the inner ring, outer ring, and cage, record those that were not peeled off when removed from the deposition chamber, and those that were peeled off as “X”, and record the results in each table. It is written together.

<Bearing life test>
The inner ring, outer ring, and cage for which a hard film was successfully formed at the film formation sites shown in each table in the above film formation test were incorporated into a 6204 rolling bearing (deep groove ball bearing) for testing and sealed with fluorine grease. A bearing for testing was used. Using this test bearing, a life test was conducted from the testing machine of FIG. The same test was performed for Comparative Example 1 in which no hard film was formed. As shown in FIG. 9, the testing machine rotates and supports a shaft that is rotated by a pulley 42 while being loaded from a load coil spring 43. 44 is a cartridge heater, and 45 is a thermocouple. Test conditions are shown below.

Inner ring / Outer ring / Cage: As shown in each table Test bearing: 6204 (Rubber seal)
Lubrication: Fluorine grease (NOXLUB KF1920 manufactured by NOK Kluber)
Enclosed amount: 5% (total space volume ratio)
Load: radial load 67N, axial load 67N
Rotation speed: 10000r / min (inner ring rotation)
Temperature: 200 ° C

  The life form is burn-in, and the torque increases rapidly as the life is reached. In this test, the time (h) until the testing machine stopped due to overload of the motor was defined as the life. The results are shown in each table.

  As shown in Table 1, it can be seen that the hard film of each example is excellent in wear resistance and adhesion. As a result, the reaction between fluorine and steel in the encapsulated fluorine grease could be suppressed, and excellent durability of 500 hours or more was shown in a life test at a high temperature (200 ° C.).

  The rolling bearing of the present invention improves the peel resistance of the DLC film formed on the inner and outer ring raceway surfaces, etc., and suppresses the reaction between fluorine and steel in the sealed fluorine grease by the film, thereby extending the life. And is excellent in seizure resistance, wear resistance, and corrosion resistance. For this reason, the rolling bearing of this invention can be utilized suitably for the use in a severe lubrication state, especially the use in a high temperature environment, a vacuum environment, etc.

1 Rolling bearing (deep groove ball bearing)
2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease 8 Hard film 11 Bias power supply 12 Base material 13 Film (layer)
DESCRIPTION OF SYMBOLS 15 Target 16 Magnetic field line 17 Ar ion 18 Ionized target 19 High density plasma 21 AIP evaporation source material 22 Disc 23 Base material 24 Sputter evaporation source material (target)
31 Test piece 32 Counterpart 33 Arm part 34 Load 35 Load cell 41 Bearing for test 42 Pulley 43 Coil spring for load 44 Cartridge heater 45 Thermocouple

Claims (21)

An inner ring having an inner ring raceway surface on the outer periphery, an outer ring having an outer ring raceway surface on the inner periphery, a plurality of rolling elements rolling between the inner ring raceway surface and the outer ring raceway surface, and a holding for holding the rolling element A rolling bearing in which fluorine grease is sealed around the rolling element,
At least one bearing member selected from the inner ring, the outer ring, the rolling element, and the cage is made of a ferrous material,
The curved surface of the bearing member made of the iron-based material, and at least one curved surface selected from the inner ring raceway surface, the outer ring raceway surface, the rolling surface of the rolling element, and the sliding surface of the cage A hard film is formed,
The hard film is a base layer mainly composed of chromium directly formed on the curved surface, a mixed layer mainly composed of tungsten carbide and diamond-like carbon formed on the base layer, A film having a structure comprising a surface layer mainly composed of diamond-like carbon formed on the mixed layer;
In the mixed layer, the content of the tungsten carbide in the mixed layer decreases continuously or stepwise from the base layer side to the surface layer side, and the diamond-like carbon in the mixed layer decreases. A rolling bearing characterized by being a layer having a high content rate.   The rolling bearing according to claim 1, wherein the rolling element is a ball, and the inner ring raceway surface and the outer ring raceway surface are circular curved surfaces that guide the rolling element.   3. The rolling bearing according to claim 1, wherein the fluorine grease is a grease containing perfluoropolyether oil as a base oil and fluorine resin powder as a thickener.   The surface layer has an inclined layer portion whose hardness increases continuously or stepwise from the mixed layer side on the side adjacent to the mixed layer. The rolling bearing described. The surface layer is a layer formed using an unbalanced magnetron sputtering apparatus using argon gas as a sputtering gas,
A graphite target and a hydrocarbon gas are used in combination as a carbon supply source, and the ratio of the introduction amount of the hydrocarbon gas to the introduction amount 100 of the argon gas into the device is 1 to 5, Under the condition that the degree of vacuum is 0.2 to 0.8 Pa and the bias voltage applied to the bearing member as the base material is 70 to 150 V, carbon atoms generated from the carbon supply source are placed on the mixed layer. The rolling bearing according to claim 1, wherein the rolling bearing is formed by deposition.   The rolling bearing according to claim 5, wherein the hydrocarbon gas is methane gas.   6. The inclined layer portion of the surface layer is formed while increasing a bias voltage applied to the bearing member serving as a base material continuously or stepwise. The rolling bearing according to claim 6. The underlayer and the mixed layer are layers formed using an unbalanced magnetron sputtering apparatus using argon gas as a sputtering gas,
The mixed layer is formed continuously or stepwise while increasing the sputtering power applied to the graphite target as a carbon supply source and decreasing the sputtering power applied to the tungsten carbide target. The rolling bearing according to any one of claims 1 to 7, characterized in that: The hard film is brought into contact with SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 by applying a load with a maximum contact surface pressure of 0.5 GPa of Hertz. The specific wear amount of the hard film when the counterpart material is rotated for 30 minutes at a rotational speed of 05 m / s is less than 200 × 10 ⁻¹⁰ mm ³ / (N · m). The rolling bearing according to any one of claims 1 to 8.   The rolling bearing according to claim 9, wherein the hard film has a total indentation hardness average value and standard deviation value of 25 to 45 GPa.   The rolling bearing according to claim 9 or 10, wherein the hard film has a critical peel load in a scratch test of 50 N or more.   The film thickness of the hard film is 0.5 to 3 µm, and the ratio of the thickness of the surface layer to the film thickness of the hard film is 0.8 or less. The rolling bearing according to claim 11.   The iron-based materials forming the inner ring, the outer ring, and the rolling elements are high carbon chromium bearing steel, carbon steel, tool steel, or martensitic stainless steel, respectively. Item 13. The rolling bearing according to any one of Items 12.   The rolling bearing according to claim 13, wherein the hardness of the curved surface on which the hard film is formed in the inner ring, the outer ring, or the rolling element is Hv 650 or more in terms of Vickers hardness.   The iron-based material forming the cage is a cold-rolled steel plate, carbon steel, chromium steel, chromium molybdenum steel, nickel chromium molybdenum steel, or austenitic stainless steel. The rolling bearing according to claim 14.   16. The rolling bearing according to claim 15, wherein in the cage, the hardness of the curved surface on which the hard film is formed is Hv450 or higher in terms of Vickers hardness.   The rolling bearing according to any one of claims 1 to 16, wherein a nitrided layer is formed by nitriding before the hard film is formed on the curved surface on which the hard film is formed.   The rolling bearing according to claim 17, wherein the nitriding treatment is a plasma nitriding treatment.   The rolling bearing according to claim 17 or 18, wherein a hardness of the curved surface after the nitriding treatment is Hv 1000 or more in terms of Vickers hardness.   20. The surface roughness Ra of the curved surface on which the hard film is formed in the inner ring, the outer ring, or the rolling element is 0.05 [mu] m or less. The rolling bearing described.   21. The rolling bearing according to claim 1, wherein a surface roughness Ra of the curved surface on which the hard film is formed in the cage is 0.5 μm or less.

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