Rolling bearing retainer and rolling bearing

Abstract

By defining the surface roughness of the retainer using multiple three-dimensional surface roughness parameters, an oil film can be maintained on the contact surface even with a small amount of lubricant, thereby providing a retainer for a rolling bearing that can maintain a stable low-friction state even under severe lubrication conditions, and a rolling bearing using the retainer. [Solution] The retainer 5 is a plastic roller bearing retainer in which a number of pockets 6 for holding the rolling elements are formed, and the value of A=(Sa / 10)+Str+(Spk / 10) calculated from the arithmetic mean height Sa on the surface 6a of the pockets 6, the aspect ratio Str of the surface texture, and the protruding peak height Spk is 1.20 or more.

Description

[Technical field]

[0001] The present invention relates to a cage for a rolling bearing, and to a rolling bearing using the cage. [Background technology]

[0002] In rolling bearings, plastic cages are widely used as cages that hold the rolling elements so that they can roll freely. Plastic cages are superior to steel cages in terms of self-lubrication, low friction characteristics, and light weight. Polyamide resins such as polyamide 66 (PA66) resin and polyamide 46 (PA46) resin are generally used as synthetic resins for plastic cages, and these are reinforced by adding fibrous reinforcing materials such as glass fiber as needed.

[0003] In recent years, there has been an increasing demand for rolling bearings used in high-speed environments such as electric vehicles and machine tools. Conventionally, air-oil lubrication has been used in many cases under high-speed rotation, but the demand for grease lubrication is increasing due to the high maintenance costs of the supply equipment. However, with grease lubrication, the grease is easily splashed off the contact surface during high-speed rotation, which can easily lead to insufficient lubrication between the rolling elements and the cage. When insufficient lubrication occurs, excessive temperature rise and wear on the contact surface lead to a shortened bearing life.

[0004] Known countermeasures for such severe lubrication conditions include forming grooves or holes on the inner peripheral surface of a pocket formed in the cage, as in Patent Document 1, and roughening the inner surface of the pocket in the cage with which the rolling elements come into contact, as in Patent Documents 2 and 3. These are intended to retain the lubricant by the shape of the cage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7088286 [Patent Document 2] JP 2014-095469 A [Patent Document 3] JP 2007-198469 A Summary of the Invention [Problem to be solved by the invention]

[0006] A plateau structure surface having recesses such as grooves or holes (a surface without protrusions, formed by a smooth surface and recesses) described in Patent Document 1 is known as a method for retaining lubricant in the recesses and improving sliding characteristics. However, when the contact conditions become more severe, such as when two surfaces come into contact with each other, such as in boundary lubrication, the plateau structure surface comes into contact with the mating surface at the smooth surface, and even if lubricant is present in the recesses, it is removed from the smooth surface, which makes it easy for the friction coefficient to increase and heat to be generated. For this reason, it is desirable for the area of ​​contact with the rolling element to be as small as possible.

[0007] In addition, in Patent Documents 2 and 3, the surface roughness (arithmetic surface roughness Ra, maximum height Rt, etc.) of the inner surface of the pocket with which the rolling elements come into contact is specified to hold the lubricant in the recesses and form a sufficient oil film. However, the parameters used in these Patent Documents are parameters determined from a two-dimensional profile curve, and are insufficient to limit the area of ​​contact with the mating surface to a small area.

[0008] The present invention has been made in consideration of the above circumstances, and has an object to provide a retainer for a rolling bearing that can maintain a stable low-friction state even under harsh lubrication conditions by defining the surface roughness of the retainer using a plurality of three-dimensional surface roughness parameters, thereby enabling an oil film to be maintained on the contact surface even with a small amount of lubricant, and a rolling bearing that uses such a retainer. [Means for solving the problem]

[0009] The present inventors have conducted extensive research focusing on three-dimensional surface roughness parameters on the surfaces of pockets of a cage for a rolling bearing, and have found that "(Sa / 10)+Str+(Spk / 10)", calculated from the arithmetic mean height Sa of the surface, the aspect ratio Str of the surface texture, and the protruding peak height Spk, shows a high correlation with the coefficient of friction, and further that a low-friction state can be controlled by specifying this value A. The present invention is based on such findings.

[0010] The retainer for a rolling bearing of the present invention is a resin retainer for a rolling bearing, characterized in that a plurality of pockets for holding rolling elements are formed in the retainer, and the value of A=(Sa / 10)+Str+(Spk / 10), calculated from the arithmetic mean height Sa of the pocket surface, the aspect ratio Str of the surface texture, and the protruding peak height Spk, is 1.20 or greater.

[0011] In one form, the above-mentioned cage is characterized in that when the contact surfaces of any one or more (for example, all) pockets in the contact surface that comes into sliding contact with the rolling element are measured so that the measurement direction of the roughness curve is perpendicular to the rotation direction of the rolling element, the surface roughness parameters calculated from ISO 25178 have a value of A = (Sa / 10) + Str + (Spk / 10) calculated from the arithmetic mean height Sa, the aspect ratio Str of the surface quality, and the protruding peak height Spk, of 1.20 or more for all the measured contact surface values ​​or their average values.

[0012] Specifically, on the contact surfaces of any one or multiple (for example, all) pockets, a point where the rolling elements and the cage can come into contact when the bearing rotates and a point 180° away from that point are set as the center point (0°) of the measurement range, and any location within a range of ±30° (measurement target area) is measured.The value of all the measured contact surfaces or their average value is characterized in that the value of A = (Sa / 10) + Str + (Spk / 10), calculated from the arithmetic mean height Sa calculated from ISO 25178, the aspect ratio Str of the surface texture, and the protruding peak height Spk, is 1.20 or more.

[0013] The aspect ratio Str is 0.80 or more. The arithmetic mean height Sa is 2.00 μm or more and 10.00 μm or less, and the protruding peak height Spk is 5.0 μm or more.

[0014] The cage is characterized in that it is an injection-molded article made of a resin composition.

[0015] The rolling bearing of the present invention is a rolling bearing having an inner ring and an outer ring, a plurality of rolling elements interposed between the inner and outer rings, a retainer that holds the rolling elements, and grease sealed in the space within the bearing, wherein the retainer is the rolling bearing retainer of the present invention.

[0016] The grease contains a base oil and a urea-based thickener, and the kinetic viscosity of the base oil at 40°C is 10mm 2 / s or more 30mm 2 / s. Effect of the Invention

[0017] The cage for a rolling bearing of the present invention has a rough surface on the surface of a pocket, and the rough surface is defined by a value A calculated from a plurality of three-dimensional surface roughness parameters calculated from a roughness curve. Specifically, by setting A=(Sa / 10)+Str+(Spk / 10), calculated from the arithmetic mean height Sa, the aspect ratio of the surface texture Str, and the protruding peak height Spk, to 1.20 or more, it becomes easier to retain lubricant, an oil film can be maintained on the contact surface even when the supply amount of lubricant is small, the contact area with the mating surface is reduced, and the friction coefficient and temperature rise are suppressed, resulting in a cage that can stably maintain a low friction state even under harsher lubrication conditions.

[0018] Since the rolling bearing of the present invention is equipped with the cage of the present invention, it is possible to achieve a longer life for the bearing even under more severe lubrication conditions. [Brief description of the drawings]

[0019] [Figure 1]1 is an axial cross-sectional view showing an example of a rolling bearing of the present invention. [Diagram 2] 1 is a perspective view showing an example of a cage for a rolling bearing of the present invention. [Diagram 3] FIG. 2 is a diagram for explaining an example of measurement locations of three-dimensional surface roughness parameters of the cage for a rolling bearing of the present invention. [Figure 4] FIG. 4 is a partially enlarged perspective view showing another example of the cage for a rolling bearing of the present invention. [Diagram 5] FIG. 1 is a diagram showing an outline of a Savin type friction and wear tester. [Figure 6] 1 is a graph showing the friction coefficients of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The cage for a rolling bearing and the rolling bearing of the present invention will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is an axial cross-sectional view showing an outline of an angular contact ball bearing, which is an example of the rolling bearing of the present invention, and Fig. 2 is a perspective view of a cage (machined type) in the rolling bearing of Fig. 1.

[0021] As shown in FIG. 1, an angular ball bearing 1 comprises an inner ring 2, an outer ring 3, a number of balls (rolling elements) 4 interposed between the inner ring 2 and the outer ring 3, and a cage 5 that holds the balls 4 at regular intervals in the circumferential direction. The inner ring 2, the outer ring 3, and the balls 4 are in contact with each other at a specific angle θ (contact angle) relative to the radial centerline, and can bear radial loads and unidirectional axial loads. In addition, the openings at both axial ends of the inner and outer rings are sealed by sealing members (not shown), and grease G is enclosed at least around the balls 4. The inner ring 2, the outer ring 3, and the balls 4 are made of an iron-based metallic material, and grease G is interposed between the raceway surfaces of the balls 4 to lubricate them.

[0022] 1, the cage 5 is of an outer ring guide type, and a part of the outer peripheral surface of the cage has an outer ring guide portion that is guided by the outer ring 3. Note that the guide type of the cage is not limited to the outer ring guide type, and may be an inner ring guide type or a rolling element guide type.

[0023] As shown in Fig. 2, the cage 5 is a machined resin cage with a ring-shaped cage body having multiple pockets 6 for holding balls spaced at regular intervals in the circumferential direction. Pillars 7 are formed between adjacent pockets 6 in the circumferential direction.

[0024] For example, the cage 5 is obtained by injection molding using a resin composition. The pocket 6 may be formed at the injection molding stage, for example, by a mold having a slide core, or may be formed by cutting after molding a base material. In the present invention, the cage 5 has a surface 6a of the pocket 6 (specifically, a contact surface that contacts the balls) that is a rough surface defined by a plurality of three-dimensional surface roughness parameters.

[0025] The rough surface may be formed, for example, by transfer from a mold, or may be formed after molding by mechanical processing such as shot blasting, filing, etc. For example, shot blasting is preferred because it is easy to obtain a processed surface that exhibits isotropy.

[0026] In the present invention, the value A=(Sa / 10)+Str+(Spk / 10) calculated from the arithmetic mean height Sa of the surface 6a, the aspect ratio Str of the surface texture, and the protruding peak height Spk is 1.20 or more.

[0027] The surface 6a for which the above value A is defined will be specifically described with reference to FIG. 3. The surface 6a is a portion that comes into contact with the balls 4, for example, a portion that comes into sliding contact with the balls 4. In this case, for example, when the surface 6a is measured in a portion of the surface 6a that comes into sliding contact with the balls 4 such that the measurement direction of the roughness curve is perpendicular to the rolling element rotation direction, the value A obtained using the surface roughness parameters obtained from ISO25178 satisfies the above range. More specifically, on the surface 6a, when one point where the balls 4 and the surface 6a can come into contact during the bearing rotation (the revolution direction (X direction) of the balls 4 in FIG. 3) and a point 180° away from the one point are set as the center point (0°) of the measurement range, and any point within a range of ±30° (region R in FIG. 3) is measured such that the measurement direction of the roughness curve is perpendicular to the rolling element rotation direction, it is preferable that the value A obtained using the surface roughness parameters obtained from ISO25178 satisfies the above range. For example, it is preferable that the value A obtained using the values ​​of all the surfaces 6a or their average value satisfies the above range.

[0028] Although FIG. 3 describes the surface 6a of one pocket, it is sufficient that the value A obtained from the surface 6a of at least one pocket in the retainer satisfies the above range. For example, the value A obtained from the surfaces of at least four pockets (pockets located at positions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees in the circumferential direction of the retainer) may satisfy the above range, or the value A obtained from the surfaces of all pockets in the retainer may satisfy the above range.

[0029] Each roughness parameter related to the value A will be described below.

[0030] [Arithmetic mean height Sa] The arithmetic mean height Sa is a parameter that expands the arithmetic mean roughness Ra into three dimensions, and is the average value of the height difference from the average surface. Because it is an average value, it is not easily affected by local scratches on the surface or dirt attached to it, so it is generally used as an index of surface roughness, and since it evaluates the surface, there is less variation depending on the measurement position compared to Ra, making it preferable for evaluating surfaces.

[0031] By increasing the arithmetic mean height Sa of the surface (for example, Sa 2.00 μm or more), the lubricant is retained in the recesses and a sufficient oil film is easily formed, compared with the case where the arithmetic mean height Sa of the surface is small (for example, Sa 1.00 μm or less). The arithmetic mean height Sa is preferably 2.00 μm or more and 10.00 μm or less, and more preferably 4.00 μm or more. On the other hand, if the arithmetic mean height Sa is large, it may affect the rotation accuracy, for example, during high-speed rotation, so Sa is preferably 8.00 μm or less, and may be less than 6.00 μm.

[0032] [Surface texture aspect ratio Str] The aspect ratio Str of the surface texture is the ratio of the distance in the direction where the surface autocorrelation decays to a specific value the fastest to the distance in the direction where it decays the slowest, and is a parameter that indicates the isotropy or anisotropy of the surface texture. The aspect ratio Str of the surface texture ranges from 0 to 1, with Str>0.5 indicating a strongly isotropic surface and Str<0.3 indicating a strongly anisotropic surface. If the aspect ratio Str of the surface texture is 0.5 or more, the lubricant on the contact surface tends to wet and spread without being biased in a specific direction, making it easier to supply the lubricant over a wide area of ​​the contact surface.

[0033] The aspect ratio Str of the surface texture is preferably 0.50 or more, and more preferably 0.80 or more.

[0034] [Protruding peak height Spk] The protruding peak height Spk is calculated from the load curve of the surface, and is the average height of the protruding peaks that are higher than the core. More specifically, for the surface to be measured, the ratio of the load area (area of ​​the area with height c or more) at a certain height c is defined as the load area ratio Smr(c), a curve (load curve) showing the height at which the load area ratio is 0% to 100% is graphed, a secant line is drawn along the load curve connecting two points where the difference in the load area ratio is 40%, and the end of the secant line is moved from the point where the load area ratio is 0%, and the position where the slope of the secant line is the gentlest is defined as the center of the load curve, and the straight line where the sum of squares of the deviation in the vertical axis direction from this center is the smallest is defined as the equivalent straight line, and the surface obtained by removing the area not included in the height range of the load area ratio of 0% to 100% of the equivalent straight line is defined as the core, and the part protruding above this core is defined as the protruding peak, and its average height is calculated. If the protruding peak height Spk is small, the protruding peak will wear away at an early stage, causing the contact surface to become flattened, increasing the contact area, and making it difficult for the lubricant to flow to the contact surface.

[0035] The protruding peak height Spk is, for example, 2.00 μm or more, preferably 4.00 μm or more, and may be 5.00 μm or more. By setting it in such a range, the contact area is reduced, and the surface becomes one into which the lubricant can easily flow. The protruding peak height Spk is, for example, 15.00 μm or less, and may be 10.00 μm or less.

[0036] Generally, surface texture is often evaluated using a single roughness parameter. However, it is preferable to evaluate using multiple parameters. In the present invention, the above-mentioned roughness parameters are combined into a formula to evaluate a surface that can maintain a low friction state even under severe lubrication conditions where only a small amount of lubricant is present. Specifically, when the value A=(Sa / 10)+Str+(Spk / 10) calculated from the arithmetic mean height Sa, the aspect ratio Str of the surface texture, and the peak height Spk is 1.20 or more, the surface has low friction even under severe lubrication conditions where only a small amount of lubricant is present.

[0037] The value A=(Sa / 10)+Str+(Spk / 10) is preferably 1.30 or more, more preferably 1.50 or more, and may be 1.70 or more. On the other hand, if the value A is too large, the surface tends to become rough, which may affect the rotation accuracy, etc., so the value A is, for example, 3.0 or less, and may be 2.5 or less.

[0038] The various roughness parameters (Sa, Str, Spk) described above are values ​​calculated in accordance with ISO25178, and are calculated from data measured by, for example, a non-contact surface roughness measuring instrument (for example, a laser microscope).

[0039] As described above, in the cage of the present invention, the arithmetic mean height Sa of the pocket surface roughness, Str indicating isotropy or anisotropy, and the parameter Spk related to the shape of the contacting protruding ridge portion are combined and defined as a formula, so that a low friction state can be maintained even under severe lubrication conditions, as shown in the examples described later.

[0040] In addition, the contact surface of the pocket with the rolling elements (see FIG. 3 for example) may have the above-mentioned roughness, or the entire surface may have the above-mentioned roughness. In addition to the pocket surface, the guide surface that comes into contact with the raceway may have the above-mentioned roughness.

[0041] In the present invention, the material of the cage may be resin, and the resin material is preferably one that can be injection molded and has sufficient heat resistance and mechanical strength as a cage material. For example, a resin composition can be used in which a PA resin such as polyether ether ketone (PEEK) resin, polyphenylene sulfide (PPS) resin, thermoplastic polyimide resin, polyamide-imide resin, PA66, PA46 resin, PA6T resin, or PA9T resin is used as the resin matrix, and reinforcing fibers such as carbon fiber and glass fiber and other additives are blended.

[0042] Returning to FIG. 1, in the angular contact ball bearing 1, both the inner ring 2 and the outer ring 3 are made of steel. Any material generally used as a bearing material can be used for the steel. For example, high carbon chromium bearing steel (SUJ1, SUJ2, SUJ3, SUJ4, SUJ5, etc.; JIS G 4805), carburized steel (SCr420, SCM420, etc.; JIS G 4053), stainless steel (SUS440C, etc.; JIS G 4303), cold rolled steel, etc. can be used. Moreover, the above steel materials or ceramic materials can be used for the balls 4. The surface roughness of the balls 4 is, for example, Ra of 0.1 μm or less.

[0043] The rolling bearing of the present invention is lubricated with grease. The grease is filled in the space inside the bearing and lubricates the raceway surface and the contact surface between the balls and the cage. As the base oil constituting the grease, any oil that is normally used in rolling bearings, such as mineral oil or synthetic oil, can be used without any particular restriction. As the thickener constituting the grease, any oil that is normally used in rolling bearings, such as metal soap or urea compound, can be used without any particular restriction.

[0044] The grease is preferably a grease containing a base oil and a urea-based thickener. In this case, the base oil is preferably a synthetic oil such as ether oil or ester oil. The kinematic viscosity of the base oil at 40°C is not particularly limited, but a base oil with a relatively low viscosity is preferable in terms of the roughness of the cage. 2 / s or more 50mm 2 / s and less than 10 mm 2 / s or more 30mm 2 / s or less is preferred.

[0045] In FIG. 1, an angular contact ball bearing has been described as an example of the rolling bearing of the present invention, however, the bearing type to which the present invention can be applied is not limited to this and the present invention can also be applied to other ball bearings, tapered roller bearings, cylindrical roller bearings, spherical roller bearings, needle roller bearings, etc.

[0046] As another example of the cage for a rolling bearing of the present invention, a crown type cage will be described with reference to Fig. 4. Fig. 4 is a partially enlarged perspective view of the crown type cage. As shown in Fig. 4, the cage 8 has a pair of opposing retaining claws 9 formed at a constant pitch in the circumferential direction on the upper surface of the annular cage body, the opposing retaining claws 9 are curved in a direction approaching each other, and a pocket 10 for holding balls as rolling elements is formed between the retaining claws 9. In addition, a flat portion 11 that serves as a rising reference surface for the retaining claws 9 is formed between the back faces of the mutually adjacent retaining claws 9 in the adjacent pockets 10. In the crown type cage 8 as well, the value A=(Sa / 10)+Str+(Spk / 10) calculated from the three-dimensional surface roughness parameters of the surface 10a of the pocket 10 is 1.20 or more.

[0047] The cage for rolling bearings of the present invention can maintain a stable low-friction state even with a small amount of lubricant, and is therefore particularly suitable for use in rolling bearings that rotate at high speeds. Specifically, it can be used in bearings used in spindle devices for machine tool main shafts and rolling bearings used in motors. For example, a cage for high-speed rotation where the dm·n value is 80×10 4 ~300×10 4 It is used in the rotation range.

[0048] The present invention is based on the fact that "(Sa / 10)+Str+(Spk / 10)", which is calculated from the arithmetic mean height Sa of the surface of the pocket of the cage for rolling bearings, the aspect ratio Str of the surface texture, and the protruding peak height Spk, shows a high correlation with the friction coefficient. Therefore, by using this as an index, the friction characteristics of the surface of the pocket of the cage for rolling bearings can be evaluated. Here, "evaluating the friction characteristics" means judging the superiority or inferiority of the degree of friction (e.g., the friction coefficient) when sliding against the rolling element.

[0049] Specifically, the evaluation method is a method for evaluating the friction characteristics between a rolling element and a resin rolling bearing retainer having a plurality of pockets formed therein for holding the rolling elements, and is characterized in that the friction characteristics on the surface of the pocket are evaluated based on the value A=(Sa / 10)+Str+(Spk / 10) calculated from the arithmetic mean height Sa on the surface of the pocket, the aspect ratio Str of the surface texture, and the protruding ridge height Spk.

[0050] The value A shows a high correlation with the coefficient of friction as shown in the examples described later (see FIG. 6). Specifically, the larger the value A, the smaller the coefficient of friction tends to be. Therefore, in the above evaluation method, the friction characteristics can be evaluated based on the magnitude of the calculated value A. For example, by comparing the value A with a predetermined threshold, if the value A is equal to or greater than the predetermined threshold, the cage can be determined to have low friction, and if the value A is less than the predetermined threshold, the cage can be determined not to have low friction. The predetermined threshold is not particularly limited, but can be set to, for example, 1.20.

[0051] Moreover, by comparing the magnitude of the value A obtained from each of a plurality of cages, it is possible to select the cage with the lowest friction. EXAMPLES

[0052] Examples of the present invention will be described below. Using a Savin type abrasion tester shown in Fig. 5, the friction coefficients of test pieces having different surface roughnesses were evaluated.

[0053] (1) Preparation of test specimens The injection molded body (composition: glass fiber reinforced polyamide 66) was cut into a size of 10 mm x 15 mm and a thickness of 4 mm to prepare a test specimen. The sliding surface of the test specimen was roughened by shot blasting and filing to obtain the test specimens of Examples 1 to 6. The test specimens of Comparative Examples 1 and 2 were not roughened, and the sliding surface was left as the injection molded surface.

[0054] (2) Measurement of roughness parameters A plurality of roughness parameters (Sa, Str, Spk) of the sliding surface of each of the test pieces obtained above were measured under the measurement conditions shown below using a laser microscope OPTELICS HYBRID manufactured by Lasertec Corporation. Measurement range: 870μm×870μm Lens magnification: 50x

[0055] The measurement results are shown in the following Table 1. The surface roughness of Comparative Examples 1 and 2 is equivalent to the roughness of a cage obtained by general injection molding.

[0056] When measuring the roughness of a cage, at least four pockets out of all pockets (e.g. pockets located at 0 degrees, 90 degrees, 180 degrees, and 270 degrees around the cage) are targeted, and in one pocket, one point where the abutment surface of the rolling element and cage pocket can come into contact when the bearing is rotating, and a point 180° away from that point are set as the center point (0°) of the measurement range, and any location within a range of ±30° is measured.

[0057] [Table 1]

[0058] (3) Saban type abrasion test A Saban type wear tester 21 shown in FIG. 5 was used. A cylindrical mating member 25 was attached to the rotating shaft, and a test piece 24 was fixed to it. A small amount of grease (0.02 g) was applied to the contact area between the test piece 24 and the cylindrical mating member 25, and no grease was supplied thereafter, simulating a state of insufficient supply of lubricant during high-speed rotation of the bearing. The cylindrical mating member 25 was brought into rotating contact with the test piece 24 while a load was applied from above in the figure by a weight 23. The frictional force generated when the cylindrical mating member 25 was rotated was detected by a load cell 22. The friction coefficient was measured 60 minutes after the start of the test. <Test conditions> Counterpart material: SUJ2 cylinder Φ40mm×10mm, arithmetic mean roughness Ra0.01μm Grease: Base oil (ester oil; kinematic viscosity at 40°C 22mm 2 / s, thickener (urea type) Relative velocity: 4.2m / s Load: 15N (surface pressure 60MPa)

[0059] The friction coefficient for each test example, measured by the Savin abrasion test, is shown in Figure 6. Figure 6 is a graph plotting the relationship between value A and the friction coefficient for each test example. As shown in Figure 6, a high correlation was observed between value A and the friction coefficient (correlation coefficient -0.91), and the larger the value A = (Sa / 10) + Str + (Spk / 10), the lower the friction coefficient. On the other hand, no correlation as strong as that with value A was observed between each three-dimensional surface roughness parameter (Sa, Str, Spk) and the friction coefficient.

[0060] As shown in Fig. 6, the friction coefficients of Examples 1 to 6 were lower than those of Comparative Examples 1 and 2, which were injection molded surfaces. Specifically, the friction coefficients of Examples 1 to 6 were less than 0.20, while those of Comparative Examples 1 to 2 were 0.20 or more. Furthermore, the friction coefficients of Examples 1 to 4 (shot blasting) were less than 0.15, compared to Examples 5 to 6 (file processing), indicating lower friction. Examples 5 to 6 had aspect ratios Str of less than 0.3, while Examples 1 to 4 had aspect ratios Str of 0.80 or more, indicating high isotropy, and it is believed that this difference influenced the low friction.

[0061] In this way, when the value A defined by the surface roughness defined in the present invention of the surface that slides against another member is large, it is possible to reduce the coefficient of friction during sliding. [Industrial Applicability]

[0062] The cage for a rolling bearing of the present invention defines the surface of the pocket face at a value A that is determined from a plurality of three-dimensional surface roughness parameters, thereby enabling an oil film to be maintained on the contact surface with even a small amount of lubricant, and enabling a stable low-friction state to be maintained even under severe lubrication conditions, making it particularly suitable for use in the field of rolling bearings that rotate at high speeds. [Explanation of symbols]

[0063] 1 Angular contact ball bearings (rolling bearings) 2. Inner Circle 3 Outer ring 4 balls (rolling elements) 5 Cage 6 Pockets 6a side 7 Pillar part 8 Cage 9 retaining claw 10 Pocket 10a side 11 Flat area 21 Saban type abrasion tester 22 Load Cell 23 Weight 24 Test Pieces 25 Cylindrical mating material

Claims

1. A resin-made rolling bearing retainer, a retainer for a rolling bearing, characterized in that a plurality of pockets for retaining rolling elements are formed in the retainer, and a value of A=(Sa / 10)+Str+(Spk / 10) calculated from an arithmetic mean height Sa of the pocket surface, an aspect ratio Str of the surface texture, and a protruding ridge height Spk is 1.20 or more.

2. 2. The cage for a rolling bearing according to claim 1, wherein the aspect ratio Str is 0.80 or more.

3. 3. The cage for a rolling bearing according to claim 2, wherein the arithmetic mean height Sa is 2.00 μm or more and 10.00 μm or less, and the protruding ridge height Spk is 5.0 μm or more.

4. 3. The cage for a rolling bearing according to claim 1, wherein the cage is an injection molded article made of a resin composition.

5. A rolling bearing having an inner ring, an outer ring, a plurality of rolling elements interposed between the inner and outer rings, a cage that holds the rolling elements, and grease sealed in a space within the bearing, 3. A rolling bearing, wherein the cage is the cage for a rolling bearing according to claim 1 or 2.

6. The grease contains a base oil and a urea-based thickener, and the kinetic viscosity of the base oil at 40°C is 10 mm ２ / s or more 30mm ２ 6. The rolling bearing according to claim 5, wherein the rolling bearing has a rolling resistance of less than 1 / s.

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