Holding tool for rolling bearing and rolling bearing

Abstract

To provide a holding tool for a rolling bearing which can stably maintain a low friction state even under a harsh lubricant condition by maintaining an oil film on a contact surface even with a small amount of lubricant by defining surface roughness of the holding tool in a plurality of three-dimensional surface roughness parameters, and a rolling bearing using the holding tool.SOLUTION: A holding tool 5 is a holding tool for a resin rolling bearing, and has a plurality of pockets 6 for holding a rolling element formed therein. A value of A=(Sa / 10)+Str+(Spk / 10) obtained from an arithmetic average height Sa on a face 6a of the pocket 6, an aspect ratio Str of a surface quality, and a projecting peak height Spk, is 1.20 or more.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] In rolling bearings, resin cages are widely used as cages for rotatably holding rolling elements. Resin cages are superior to iron cages in terms of self-lubricity, low friction characteristics, light weight, etc. As the synthetic resin of the resin cage, polyamide resins such as polyamide 66 (PA66) resin and polyamide 46 (PA46) resin are generally used, and those containing fibrous reinforcing materials such as glass fibers and strengthened as necessary are used.

[0003] In recent years, the demand for rolling bearings used in high-speed environments such as electric vehicles and machine tools has been increasing. Conventionally, air-oil lubrication is often used under high-speed rotation, but due to the high maintenance cost of the supply equipment, the demand for grease lubrication is increasing. However, in the case of grease lubrication, the grease is easily bounced off from the contact surface during high-speed rotation, and lubrication deficiency is likely to occur between the rolling elements and the cage. And when lubrication deficiency occurs, it leads to a reduction in the bearing life due to excessive temperature rise and wear on the contact surface.

[0004] As countermeasures under such severe lubrication conditions, for example, as in Patent Document 1, those in which grooves or holes are formed on the inner peripheral surface of the pockets formed in the cage, or as in Patent Documents 2 and 3, those in which the inner surface of the pockets where the rolling elements contact in the cage is roughened are known. These aim to hold the lubricant depending on the shape of the cage.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] The plateau structure surface having recesses such as grooves or holes described in Patent Document 1 (a surface formed of a smooth surface and recesses without protrusions) can hold a lubricant in the recesses and is known as a method for improving sliding characteristics. However, when the contact conditions become more severe, such as in boundary lubrication where two surfaces come into contact, the plateau structure surface comes into contact with the mating surface on the smooth surface, and even if there is a lubricant in the recesses, it is removed from the smooth surface, so an increase in the friction coefficient and heat generation are likely to occur. Therefore, it is desirable that the area of contact with the rolling elements be as small as possible.

[0007] Also, in Patent Documents 2 and 3, the surface roughness (such as the arithmetic surface roughness Ra and the maximum height Rt) of the inner surface of the pocket with which the rolling elements come into contact is defined so that a sufficient oil film is formed by holding a lubricant in the recesses. However, the parameters used in these patent documents are parameters determined from two-dimensional contour curves and are insufficient for severely limiting the area of contact with the mating surface.

[0008] The present invention has been made in view of such circumstances, and by defining the surface roughness of the cage with a plurality of three-dimensional surface roughness parameters, it is possible to maintain an oil film on the contact surface even with a small amount of lubricant, and to provide a rolling bearing cage capable of stably maintaining a low-friction state even under severe lubrication conditions, and a rolling bearing using the cage. [Means for Solving the Problems]

[0009] The inventors of the present invention have conducted intensive studies focusing on the three-dimensional surface roughness parameters on the surface of the pockets of a rolling bearing cage. As a result, it has been found that “(Sa / 10)+Str+(Spk / 10)” obtained from the arithmetic mean height Sa, the aspect ratio Str of the surface texture, and the peak height Spk of the protruding peaks of the surface shows a high correlation with the friction coefficient. Furthermore, it has been found that a low-friction state can be controlled by defining the value A thereof. The present invention is based on such findings.

[0010] The rolling bearing cage of the present invention is a resin-made rolling bearing cage, in which a plurality of pockets for holding rolling elements are formed in the cage, and the value of A = (Sa / 10)+Str+(Spk / 10) obtained from the arithmetic mean height Sa, the aspect ratio Str of the surface texture, and the peak height Spk of the protruding peaks on the surface of the pockets is 1.20 or more.

[0011] As one embodiment, when measuring the contact surfaces of any one or more (for example, all) of the pockets such that the measurement direction of the roughness curve is perpendicular to the rolling element rotation direction on the contact surface that slidably contacts the rolling element, for the surface roughness parameters obtained from ISO25178, the value of A = (Sa / 10)+Str+(Spk / 10) obtained from the arithmetic mean height Sa, the aspect ratio Str of the surface texture, and the peak height Spk of the protruding peaks is 1.20 or more in the values of all the measured contact surfaces or the average value thereof.

[0012] Specifically, on the contact surface of any one or more (for example, all) of the pockets, when measuring an arbitrary position within the range of ±30° (measurement target area) with one point where the rolling element and the cage may come into contact during bearing rotation and a point 180° away from that point as the center points (0°) of the measurement range respectively, the value of A = (Sa / 10)+Str+(Spk / 10) obtained from the arithmetic mean height Sa, the aspect ratio Str of the surface texture, and the peak height Spk of the protruding peaks obtained from ISO25178 is 1.20 or more in the values of all the measured contact surfaces or the average value thereof.

[0013] It is characterized in that the aspect ratio Str is 0.80 or more. Further, the arithmetic mean height Sa is 2.00 μm or more and 10.00 μm or less, and the protrusion peak height Spk is 5.0 μm or more.

[0014] The cage is an injection molded body of a resin composition.

[0015] The rolling bearing of the present invention is a rolling bearing having an inner ring, an outer ring, a plurality of rolling elements interposed between the inner and outer rings, a cage for holding the rolling elements, and grease enclosed in the bearing inner space, characterized in that the cage is a cage for a rolling bearing of the present invention.

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

Advantages of the Invention

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

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

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

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

[0021] As shown in FIG. 1, the angular ball bearing 1 includes an inner ring 2, an outer ring 3, a plurality 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 predetermined angle θ (contact angle) with respect to the radial center line, and can bear a radial load and a unidirectional axial load. Further, both axial end openings of the inner and outer rings are sealed by a seal member (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 metal material, and the grease G is interposed between the ball 4 and the raceway surface for lubrication.

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

[0023] As shown in Fig. 2, the cage 5 is a resin cage of a threshing type, and a plurality of pockets 6 for holding balls are provided at regular intervals in the circumferential direction in an annular cage body. A column portion 7 is formed between the pockets 6 adjacent 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, for example, in an injection molding stage by a mold having a slide core, or may be formed by cutting after molding a blank. In the present invention, in the cage 5, the surface 6a of the pocket 6 (specifically, the contact surface that contacts the ball) is a rough surface defined by a plurality of three-dimensional surface roughness parameters.

[0025] The above-mentioned rough surface may be formed, for example, by transfer from a mold, or may be formed by machining such as shot blasting or filing after molding. For example, shot blasting is preferable because it is easy to obtain a processed surface showing isotropy.

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

[0027] The surface 6a on which the above-mentioned value A is defined will be specifically described with reference to FIG. 3. The surface 6a is the portion that contacts the ball 4, for example, the portion that slides in contact with the ball 4. In this case, for example, when the surface 6a is measured such that the measurement direction of the roughness curve is perpendicular to the rolling element rotation direction at the portion where the surface 6a slides in contact with the ball 4, the value A obtained using the surface roughness parameters determined from ISO 25178 satisfies the above range. More specifically, on the surface 6a, one point where the ball 4 and the surface 6a can come into contact during bearing rotation (the revolution direction (X direction) of the ball 4 in FIG. 3) and a point 180° away from that point are each taken as the center point (0°) of the measurement range, and when any location within the 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 determined from ISO 25178 satisfies the above range. For example, it is preferable that the value A obtained using all the values of the surface 6a or their average value satisfies the above range.

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

[0029] Hereinafter, each roughness parameter related to the value A will be described.

[0030] [Arithmetic mean height Sa] The arithmetic mean height Sa is a parameter obtained by three-dimensionally expanding the arithmetic mean roughness Ra and is the average value of the height differences from the average surface. Since it is an average value, it is less affected by local scratches on the surface and adhered dust, etc., and is generally used as an index of surface roughness. Compared with Ra for evaluating the surface, the variation due to the measurement position is smaller, which is preferable for evaluating the surface.

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

[0032] [Aspect ratio Str of surface texture] 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 most quickly and the distance in the direction where it decays most slowly, and is a parameter representing the isotropy and anisotropy of the surface texture. The aspect ratio Str of the surface texture takes a value in the range of 0 to 1. When Str > 0.5, it indicates a strongly isotropic surface, and when Str < 0.3, it indicates a strongly anisotropic surface. If the surface texture has an aspect ratio Str of 0.5 or more, the lubricant on the contact surface is likely to spread wet without being biased in a specific direction, so it becomes easier to supply the lubricant to a wide range of the contact surface.

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

[0034] [Peak height Spk] The height Spk of the protruding peaks is obtained from the load curve of the surface and is the average height of the protruding peaks, which are higher than the core part. More specifically, for the surface to be measured, the ratio of the load area (the area of the region with a height of c or more) at a certain height c is defined as the load area ratio Smr(c). A curve (load curve) representing the height at which the load area ratio ranges from 0% to 100% is graphed. A secant line is drawn by connecting two points where the difference in the load area ratio along the load curve is 40%. As the end of the secant line is moved from the point where the load area ratio is 0%, the position where the slope of the secant line becomes the gentlest is defined as the central part of the load curve. For this central part, a straight line with the minimum sum of the squared deviations in the vertical axis direction is defined as the equivalent line. The surface obtained by removing the region not included in the height range from 0% to 100% of the load area ratio of the equivalent line is defined as the core part, and the part protruding upward from this core part is defined as the protruding peaks, and its average height is determined. When the height Spk of the protruding peaks is small, the protruding peaks wear at the initial stage, and the contact surface flattens, increasing the contact area and making it difficult for the lubricant to flow into the contact surface.

[0035] The height Spk of the protruding peaks 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 within such a range, the contact area can be reduced, and the surface becomes one where the lubricant can easily flow in. Also, the height Spk of the protruding peaks is, for example, 15.00 μm or less, and may be 10.00 μm or less.

[0036] Generally, surface properties are often evaluated using a single roughness parameter. However, it is preferable to evaluate using a plurality of parameters. In the present invention, particularly by combining the above-described roughness parameters as mathematical expressions, a surface that can maintain a low-friction state even under severe lubrication conditions where only a small amount of lubricant exists can be evaluated. Specifically, a value A = (Sa / 10) + Str + (Spk / 10) obtained from the arithmetic mean height Sa, the aspect ratio Str of the surface properties, and the height Spk of the protruding peaks being 1.20 or more results in a low-friction surface even under severe lubrication conditions where only a small amount of lubricant exists.

[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 becomes too large, the surface tends to become rough, which may affect the rotational accuracy and the like. Therefore, the value A is, for example, 3.0 or less, and may be 2.5 or less.

[0038] Each of the above-described roughness parameters (Sa, Str, Spk) is a numerical value calculated in accordance with ISO25178, and is calculated from data measured by, for example, a non-contact surface roughness measuring instrument (e.g., a laser microscope).

[0039] As described above, in the cage of the present invention, by combining the arithmetic mean height Sa, Str indicating isotropy or anisotropy, and Spk, a parameter related to the shape of the contacting protrusions, of the surface of the pocket as a mathematical formula, as shown in the following examples, even under severe lubrication conditions, a low friction state can be maintained.

[0040] In addition, on the surface of the pocket, the contact surface (see, for example, FIG. 3) with which the rolling element contacts may have the above-described roughness, or the entire surface may have the above-described roughness. Further, in addition to the surface of the pocket, the guide surface that contacts the raceway ring may have the above-described roughness.

[0041] In the present invention, the material of the cage may be made of resin. As the resin material, those capable of injection molding and having sufficient heat resistance and mechanical strength as a cage material are preferable. For example, a resin composition in which a PA resin such as polyetheretherketone (PEEK) resin, polyphenylene sulfide (PPS) resin, thermoplastic polyimide resin, polyamideimide resin, PA66, PA46 resin, PA6T resin, PA9T resin is used as a resin base material, and reinforcing fibers such as carbon fiber and glass fiber, and other additives are blended can be used.

[0042] Returning to FIG. 1, in the angular 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 (such as SUJ1, SUJ2, SUJ3, SUJ4, SUJ5; JIS G 4805), carburized steel (such as SCr420, SCM420; JIS G 4053), stainless steel (such as SUS440C; JIS G 4303), cold-rolled steel, etc. can be used. Also, for the balls 4, the above-mentioned steel materials or ceramic materials can be used. The surface roughness of the balls 4 is, for example, Ra is 0.1 μm or less.

[0043] The rolling bearing of the present invention is lubricated with grease. The grease is enclosed in the bearing inner space and lubrication is performed through its interposition between the raceway surfaces, the contact surfaces of the balls and the cage, etc. As the base oil constituting the grease, mineral oil, synthetic oil, etc., as long as it is usually used for rolling bearings, can be used without particular limitation. Also, as the thickener constituting the grease, metal soap, urea compound, etc., as long as it is usually used for rolling bearings, can be used without particular limitation.

[0044] Preferably, the grease is 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 relatively low-viscosity base oil is preferred due to the relationship with the roughness of the cage. For example, it is 10 mm 2 / s or more and 50 mm 2 / s less, and 10 mm 2 / s or more and 30 mm 2 / s less is preferred.

[0045] In FIG. 1, the angular ball bearing is described as an example of the rolling bearing of the present invention, but the bearing type to which the present invention can be applied is not limited to this, and it can also be applied to other ball bearings, tapered roller bearings, cylindrical roller bearings, self-aligning roller bearings, needle roller bearings, etc.

[0046] As another example of the cage for a rolling bearing of the present invention, a crowned cage will be described with reference to FIG. 4. FIG. 4 is a partially enlarged perspective view of the crowned cage. As shown in FIG. 4, the cage 8 forms a pair of opposing retaining claws 9 at regular circumferential pitches on the upper surface of the annular cage body, bends each of the opposing retaining claws 9 in a direction approaching each other, and forms pockets 10 for holding balls as rolling elements between the retaining claws 9. Further, flat portions 11 serving as rising reference surfaces of the retaining claws 9 are formed between the back surfaces of the mutually adjacent retaining claws 9 in adjacent pockets 10. Also in the crowned cage 8, the value A = (Sa / 10) + Str + (Spk / 10) obtained from each three-dimensional surface roughness parameter of the surface 10a of the pocket 10 is 1.20 or more.

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

[0048] The present invention is based on the fact that "(Sa / 10) + Str + (Spk / 10)" obtained from the arithmetic mean height Sa of the surface in the pocket of the cage for a rolling bearing, the aspect ratio Str of the surface texture, and the height Spk of the protruding peaks 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 a rolling bearing can be evaluated. Here, "evaluating the friction characteristics" means judging the superiority or inferiority of the degree of friction (for example, the friction coefficient) when sliding with the rolling element.

[0049] Specifically, the above evaluation method is a method for evaluating the friction characteristics with the rolling elements in a resin rolling bearing cage in which a plurality of pockets for holding the rolling elements are formed, and is a method for evaluating the friction characteristics with the rolling elements. Based on the value of A = (Sa / 10) + Str + (Spk / 10) obtained from the arithmetic mean height Sa, the aspect ratio Str of the surface texture, and the height Spk of the protruding peaks on the surface of the pocket, the friction characteristics on the surface of the pocket are evaluated.

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

[0051] Also, by comparing the magnitudes of the values of A obtained from each of the plurality of cages, the cage with the lowest friction can be selected.

Examples

[0052] Hereinafter, examples of the present invention will be described. Using the Saban type wear tester shown in Fig. 5, the friction coefficients of test pieces with different surface roughnesses were evaluated respectively.

[0053] (1) Preparation of test pieces An injection-molded molded body (composition: glass fiber-reinforced polyamide 66) was cut into 10 mm × 15 mm with a thickness of 4 mm to prepare test pieces. The sliding surfaces of the test pieces were roughened by shot blasting and filing to obtain the test pieces of Examples 1 to 6 respectively. Note that the test pieces of Comparative Examples 1 and 2 were not roughened, and the sliding surfaces remained as the injection-molded surfaces.

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

[0055] The measurement results are shown in Table 1 below. The surface roughnesses of Comparative Examples 1 and 2 are equivalent to those of cages obtained by general injection molding.

[0056] When measuring the roughness of the cage, at least four pockets in all pockets (for example, pockets located at 0°, 90°, 180°, and 270° in the circumferential direction of the cage) are targeted. In one pocket, one point where the contact surface between the rolling element and the pocket of the cage may come into contact during bearing rotation and a point 180° away from that point are each taken as the center point (0°) of the measurement range, and arbitrary locations within the range of ±30° are measured.

[0057]

Table 1

[0058] (3) SAE type wear test The SAE type wear test machine 21 shown in Fig. 5 was used. A cylindrical mating material 25 was attached to the rotating shaft, and the test piece 24 was fixed. A small amount (0.02 g) of grease was attached to the contact portion between the test piece 24 and the cylindrical mating material 25, and after that, no supply was made to simulate the insufficient supply state of the lubricant during high-speed rotation of the bearing. The cylindrical mating material 25 was brought into rotational contact with the test piece 24 while a load was applied from above the drawing by the weight 23. The frictional force generated when the cylindrical mating material 25 was rotated was detected by the load cell 22. The friction coefficient was measured at the value after 60 minutes from the start of the test. <Test conditions> Mating material: Cylindrical SUJ2, Φ40 mm × 10 mm, arithmetic mean roughness Ra 0.01 μm Grease: Base oil (ester oil; kinematic viscosity at 40°C 22 mm 2 / s, swelling agent (urea-based) Relative speed: 4.2 m / s Load: 15 N (surface pressure 60 MPa)

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

[0060] As shown in Fig. 6, Examples 1 to 6 had lower friction coefficients compared to Comparative Examples 1 and 2, which are injection-molded surfaces. Specifically, the friction coefficients of Examples 1 to 6 were less than 0.20, while those of Comparative Examples 1 and 2 were 0.20 or more. Furthermore, compared with Examples 5 to 6 (file finishing), the friction coefficients of Examples 1 to 4 (shot blasting) were less than 0.15, showing lower friction. Examples 5 to 6 had an aspect ratio Str of less than 0.3, while Examples 1 to 4 had a high isotropy with an aspect ratio Str of 0.80 or more, and this difference is considered to have affected the low friction property.

[0061] Thus, when the value A defined from the surface roughness determined by the present invention for the surface that slides with other members is large, it is possible to lower the friction coefficient during sliding.

Industrial Applicability

[0062] By defining the surface of the pocket of the rolling bearing retainer of the present invention with the value A determined from a plurality of three-dimensional surface roughness parameters, it is possible to maintain an oil film on the contact surface even with a small amount of lubricant, and it is possible to stably maintain a low friction state even under severe lubrication conditions. Therefore, it can be used particularly in the field of rolling bearings that rotate at high speed.

Explanation of Signs

[0063] 1 Angular ball bearing (rolling bearing) 2 Inner ring 3 Outer ring 4 Balls (rolling elements) 5 Cage 6 Pocket 6a Surface 7 Column part 8 Cage 9 Retaining claw 10 Pocket 10a Surface 11 Flat part 21 Saban type wear test machine 22 Load cell 23 Weight 24 Test piece 25 Cylindrical mating material

Claims

1. A resin rolling bearing cage, wherein a plurality of pockets for holding rolling elements are formed in the cage, and the value of A = (Sa / 10) + Str + (Spk / 10) obtained from the arithmetic mean height Sa, the aspect ratio Str of the surface texture, and the protruding peak height Spk on the surface of the pocket is 1.20 or more. The rolling bearing cage is characterized by this.

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

3. The rolling bearing cage 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 peak height Spk is 5.0 μm or more.

4. The rolling bearing cage according to claim 1 or claim 2, wherein the cage is an injection molded body 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 for holding the rolling elements, and grease enclosed in the bearing inner space, wherein the cage is the rolling bearing cage according to claim 1 or claim 2. The rolling bearing is characterized by this.

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

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