JP2011208781A - Anti-friction bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-friction bearing that achieves improvement in peel resistance of a DLC film formed on the sliding contact surface of a retainer of the anti-friction bearing and allows exertion of the original properties of the DLC film, and consequently, prevents damage or the like caused by a metal-to-metal contact of the sliding contact surface of the retainer.SOLUTION: The anti-friction 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, a plurality of rolling elements 4 that roll between the inner-ring raceway surface 2a and the outer-ring raceway surface 3a, and a retainer 5 for retaining the rolling elements 4 at fixed intervals. A hard film 8 is formed on the sliding contact surface with the rolling elements 4 of the retainer 5. The hard film 8 is a film having a structure comprising a base layer which is directly film-formed on the sliding contact surface and mainly composed of Cr, a mixed layer which is film-formed on the base layer and mainly composed of WC and DLC, and a surface layer which is film-formed on the mixed layer and mainly composed of DLC. The mixed layer is a layer configured such that the content rate of the WC is reduced continuously or stepwise but the content rate of the 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 in which a hard film containing diamond-like carbon is formed on the sliding contact surface of a cage of the rolling bearing.

  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 the cage sliding surface of the rolling bearing. 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 in sliding contact parts, such as a cage sliding contact surface of a rolling bearing, it is necessary to improve adhesiveness.

  For example, assuming that the adhesion of a hard film such as a DLC film is improved by providing an intermediate layer, a multi-layered film is formed on the surface of the cage of the rolling bearing, and the space between the outermost layer film and the cage In addition, a cage has been proposed in which an intermediate layer having a predetermined hardness is interposed (see Patent Document 1). Further, 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 2 and Patent Document 3).

JP 2006-3000294 A Japanese Patent Laying-Open No. 2005-147306 JP 2005-147244 A

  However, the sliding contact surface of the cage in the rolling bearing is a surface in contact with the rolling element or a surface in contact with the raceway, and the surface in contact with the raceway is a curved surface. Moreover, the surface which contacts a rolling element is a cage | basket pocket surface, and there exist things, such as a shape etc. which combined the main curvature and the subcurvature as this shape. When the DLC film is formed on the sliding contact surface having such a shape, the residual stress in the film increases depending on the film structure and film formation conditions, and there is a possibility that the film is peeled off immediately after the film formation. In addition, the cage sliding contact surface of a rolling bearing is subjected to an impact force or a thermal shock due to local sliding heat generation. There is a risk.

  When the DLC film is peeled from the cage, metal contact occurs with the rolling elements, and wear of the cage or rolling elements causes wear powder to intervene on the rolling surface, leading to raceway damage. In the case of grease lubrication, grease degradation may be promoted by the catalytic action of the new metal surface.

  The technology of each of the above-mentioned patent documents is intended to prevent the hard film from peeling, but in order to improve the practicality of the obtained rolling bearing, the film structure when applying the DLC film to the cage sliding surface There is room for further improvement in film formation conditions.

  The present invention has been made to cope with such problems, and improves the peel resistance of the DLC film formed on the sliding contact surface of the cage of the rolling bearing, and exhibits the original characteristics of the DLC film. Then, it aims at provision of the rolling bearing which can prevent the damage resulting from the metal contact of a cage sliding surface.

  The rolling bearing of the present invention is a rolling bearing comprising an inner ring and an outer ring that are raceways, a plurality of rolling elements interposed between the inner and outer rings, and a cage made of an iron-based material that holds the rolling elements. The cage is formed by forming a hard film on at least one sliding contact surface selected from the sliding contact surface with the raceway and the sliding contact surface with the rolling element. An underlayer mainly composed of Cr formed directly on the sliding surface, and a mixed layer mainly composed of tungsten carbide (hereinafter referred to as WC) and DLC formed on the underlayer. , A film composed of a surface layer mainly composed of DLC formed on the mixed layer, and the mixed layer is continuously or stepwise from the base layer side to the surface layer side. , The content of WC in the mixed layer is reduced, and the content of DLC in the mixed layer is Characterized in that it is a Kunar layer.

  The rolling element is a ball, and the hard film in the cage is formed on a pocket surface that holds the ball, which is a sliding surface with the rolling element.

  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 cage is 70 to 150V. Further, the hydrocarbon gas is methane gas.

  Note that the bias potential applied to the cage 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 with respect to the ground potential. Indicates that

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

  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 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 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 addition, the sliding contact surface on which the hard film is formed has a Vickers hardness of Hv450 or more.

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

  The surface roughness Ra of the sliding contact surface on which the hard film is formed is 0.5 μm or less.

  The rolling bearing is characterized in that grease is enclosed.

  In the rolling bearing of the present invention, a hard film having a predetermined film structure including DLC is formed on at least one sliding contact surface selected from a sliding contact surface with a raceway ring and a sliding contact surface with a rolling element in an iron cage. It is made a film. The underlayer made of Cr formed directly on each sliding contact 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 is excellent in peel resistance while being formed on a non-planar cage sliding surface, and can exhibit the original characteristics of DLC. As a result, the rolling bearing of the present invention can prevent damage caused by metal contact on the cage sliding surface even under severe lubrication, and has a long life.

It is sectional drawing which shows an example of the rolling bearing of this invention. It is an enlarged view of a holder | retainer. 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 with no delamination immediately after film formation and a large critical delamination load in a scratch test peels off immediately after film formation on a curved surface such as a cage pocket surface of a rolling bearing, or immediately after film formation. Even if it does not peel, it may be easily peeled off during use. As a result of intensive studies, the present inventors have determined that a hard film to be formed on a cage sliding surface (such as a pocket surface) of a rolling bearing is a base layer (Cr), a mixed layer (WC / DLC slope), and a surface layer ( It has been found that by limiting to a predetermined structure consisting of DLC), the peel resistance can be greatly improved, and the hard film can be prevented from peeling even under actual use conditions of the bearing. The present invention has been made based on such findings.

  The rolling bearing of the present invention will be described with reference to FIGS. FIG. 1 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. 2 is an enlarged view of the cage. 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 opening portions in the axial direction of the inner and outer rings are sealed by the seal member 6, and grease 7 is sealed in the bearing space. As the grease 7, a known grease for a rolling bearing can be used.

  As shown in FIG. 2, the cage 5 is a corrugated iron plate cage, which is manufactured by combining two members 5 a and 5 a that are press-molded using an iron-based material described later. A holder pocket 5b for holding is formed. 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 ring (inner ring 2 or outer ring 3) and the sliding contact surface with the rolling element 4.

  In the rolling bearing 1 of the present invention, the cage 5 that is the target for forming the hard film 8 is made of an iron-based material. As the iron-based material, any material generally used as a cage material can be used, for example, cold rolled steel sheet, carbon steel, chrome steel, chrome molybdenum steel, nickel chrome molybdenum steel, austenitic stainless steel, etc. It is done.

  In this cage 5, it is preferable that the hardness of the sliding contact surface on which the hard film 8 is formed is Hv450 or higher in terms of Vickers hardness. By setting it as Hv450 or more, a hardness difference with a hard film | membrane (underlayer) can be decreased and adhesiveness can be improved.

  In the slidable contact surface on which the hard film 8 is formed, a nitride layer is preferably 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 formed on the surface of the cage. Further, the surface hardness after nitriding is preferably Vickers hardness of Hv1000 or more in order to further improve the adhesion to the hard film (underlayer).

  The surface roughness Ra of the slidable contact 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.

  The structure of the hard film in the present invention will be described with reference to FIG. FIG. 3 is a schematic cross-sectional view showing the structure of the hard film 8 in the case of FIG. As shown in FIG. 3, the hard film 8 includes (1) an underlayer 8a mainly composed of Cr and formed directly on the sliding contact surface (pocket surface) with the rolling element in the cage 5, and (2 3) Three layers comprising a mixed layer 8b mainly composed of WC and DLC formed on the base layer 8a, and (3) a surface layer 8c mainly composed of DLC formed on the mixed layer 8b. It has a structure. 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 foundation layer 8a is a layer mainly composed of Cr, the compatibility with the cage 5 made of an iron-based material as a base material is good, and compared with the case where W, Ti, Si, or the like is used, Excellent adhesion.

  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. As shown in Comparative Example 7 which will be described later, in the case where the mixed layer is a layer mainly composed of Cr and DLC in accordance with the base layer, the adhesion when using the bearing is not sufficient. As described above, when a hard film containing DLC having excellent peeling resistance is to be formed on the roller sliding contact surface of the rolling bearing, material selection in the intermediate layer (mixed layer 8b) 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 layer 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 to the substrate is different between the mixed layer 8b and the surface layer 8c. It is. 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 mating material is small, and the specific wear amount in this test is 200 × 10 ⁻¹⁰ mm ³ / (N · m If it is less than (), it is effective in reducing wear even against local slip generated on 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 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 peeling load is less than 50 N, there is a high possibility that the hard film peels when the contact stress on the sliding surface is high. 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 properties as described above, the film can be peeled off even when a shock is applied or a thermal shock due to local sliding heat generation is applied during use of the bearing. It can be prevented, and even under severe lubrication conditions, there is little bearing damage and the service life is long. In addition, when a new metal surface is exposed due to metal contact in a rolling bearing encapsulated with grease, grease degradation is promoted by catalytic action. However, in the rolling bearing of the present invention, the raceway surface or rolling due to metal contact with the cage is caused by a hard film. Since the moving surface can be prevented from being damaged, this grease deterioration can also be prevented.

  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 sliding surface of the cage.

  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 cage to be deposited, but is schematically shown as a flat plate. As shown in FIG. 4, an inner magnet 14 a and an outer magnet 14 b having different magnetic properties 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.

  As described above, the bias voltage applied to the cage as the substrate is preferably 70 to 150V. 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 a film while increasing the bias voltage applied to the cage as the base material continuously or stepwise.

  As the hard film formed on the cage of the rolling bearing of the present invention, a hard film is formed on a predetermined base material, and the physical properties of the hard film are evaluated, and the same hard film is applied to the cage bearing of the rolling bearing. A film was actually formed on the contact surface, 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: SUS440C, SUJ2, S53C
(2) Base material dimensions: Mirror surface (Ra 0.005 μm) disc (φ48 mm × φ8 mm × 7 mm)
(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.
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.
(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. 5 is a schematic diagram of a UBMS apparatus having an arc ion plating (hereinafter referred to as AIP) function. As shown in FIG. 5, the UBMS 202 / AIP composite apparatus instantaneously vaporizes and ionizes the AIP evaporation source material 21 to the base material 23 arranged on the disk 22 using vacuum arc discharge, 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. 4), the apparatus has a UBMS function capable of controlling the characteristics of the film deposited on the 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 cage as a base material.

Example 1 to Example 9, Example 11, Comparative Example 1 to Comparative Example 7, Reference Example 1 to Reference Example 7
The substrates shown in Tables 1 to 3 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. 6A shows a front view, and FIG. 6B 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 side 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>
About the obtained test piece, the scratch test was done using the nanotech company make: level test RST, and the critical peeling 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.

<Deposition test on bearing cage>
Film formation was actually performed on the following cage sliding contact surface (pocket surface) for 6204 rolling bearing (deep groove ball bearing) under each condition of Example, Comparative Example, and Reference Example. The peeling of the hard film was confirmed. Those that were not peeled when removed from the film forming chamber were recorded as “◯”, and those that were peeled off were recorded as “X”, and the results are shown in each table.
Cage: Steel plate cage with two cracks (Hard film is formed on the sliding contact surface with the rolling element. Cage base material (material, hardness, surface roughness) is as shown in Table 1)

<Bearing life test>
A test 6204 rolling bearing (deep groove ball bearing) was assembled by using the inner and outer rings of Examples 1 to 11 and Comparative Example 7 in which a hard film was formed in the film formation test, and this test bearing was used for illustration. A life test was conducted from 7 testing machines. As shown in FIG. 7, the testing machine rotates and supports a shaft 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.

Cage: Steel plate cage with two cracks (Hard film is formed on the sliding contact surface with the rolling element. Cage base material (material, hardness, surface roughness) is as shown in Table 1)
Test bearing: 6204 (rubber seal)
Lubrication: Lithium ester grease (base oil viscosity at 40 ° C 26mm ² / s, miscibility of 260)
Enclosed amount: 15% (total space volume ratio)
Load: radial load 67N, axial load 67N
Rotation speed: 10000r / min (inner ring rotation)
Temperature: 150 ° 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 Tables 1 and 2.

  As shown in Table 1, the hard film of each example was excellent in wear resistance and adhesion, and even when the bearing was used, the hard film could be prevented from peeling from the cage.

  The rolling bearing of the present invention is excellent in the peel resistance of the hard film containing DLC formed on the cage sliding surface and can exhibit the characteristics of the DLC main body, so that damage caused by metal contact on the cage sliding surface, etc. Can be prevented and has a long life. For this reason, the rolling bearing of this invention is applicable to various uses including the use in a severe lubrication state.

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 (18)

A rolling bearing comprising an inner ring and an outer ring that are raceways, a plurality of rolling elements interposed between the inner and outer rings, and a cage made of an iron-based material that holds the rolling elements,
The cage is formed by forming a hard film on at least one sliding contact surface selected from a sliding contact surface with the raceway and a sliding contact surface with the rolling element,
The hard film includes a base layer mainly composed of chromium directly formed on the sliding contact surface, and a mixed layer mainly composed of tungsten carbide and diamond-like carbon formed on the base layer. And a film having a structure composed of 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 said rolling element is a ball | bowl, The said hard film | membrane in the said holder | retainer is formed into a film in the pocket surface holding the said ball | bowl which is a sliding contact surface with the said rolling element. Rolling bearing.   The rolling bearing according to claim 1, wherein the surface layer has an inclined layer portion whose hardness increases continuously or stepwise from the mixed layer side on a side adjacent to the mixed layer. . 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 cage as the base material is 70 to 150 V, carbon atoms generated from the carbon supply source are placed on the mixed layer. 4. The rolling bearing according to claim 1, wherein the rolling bearing is formed by being deposited.   The rolling bearing according to claim 4, wherein the hydrocarbon-based gas is methane gas.   The inclined layer portion of the surface layer is formed by increasing a bias voltage applied to the cage as a base material continuously or stepwise, or 3 or 4 or The rolling bearing according to claim 5. 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 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 tungsten carbide target. The rolling bearing according to any one of claims 1 to 6, wherein the rolling bearing is characterized. 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 7.   The rolling bearing according to claim 8, 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 8 or 9, 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 10.   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 11.   The rolling bearing according to claim 12, wherein the sliding surface on which the hard film is formed has a Vickers hardness of Hv450 or more.   The rolling bearing according to any one of claims 1 to 13, wherein a nitrided layer is formed by nitriding treatment on the sliding contact surface on which the hard film is formed before the hard film is formed. .   The rolling bearing according to claim 14, wherein the nitriding treatment is a plasma nitriding treatment.   The rolling bearing according to claim 14 or 15, wherein a hardness of the surface after the nitriding treatment is Hv1000 or more in terms of Vickers hardness.   The rolling bearing according to any one of claims 1 to 16, wherein a surface roughness Ra of a sliding contact surface on which the hard film is formed is 0.5 µm or less.   The rolling bearing according to claim 1, wherein the rolling bearing is filled with grease.

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