Holder for rolling bearing, and rolling bearing

Abstract

To provide a holder for a rolling bearing that can maintain an oil film on a contact surface even with a small amount of lubricant by regulating the surface roughness of a pocket surface with a plurality of rough parameters, and can maintain a low-friction state stably even under severe lubrication conditions, and a rolling bearing using the holder.SOLUTION: A holder 5 is a resin holder for a rolling bearing, has a plurality of pockets 6 for holding rolling elements, where arithmetic average roughness Ra acquired from a rough curve in surface roughness of the pocket 6a contacting with the rolling element in the pocket 6 is 3.00 μm or more and 10.00 μm or less, the average length RSm of the elements is 0.10 mm or more and 0.40 mm or less, and the kurtosis Rku is 1.0 or more and 5.0 or less.SELECTED DRAWING: Figure 2

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, for example, forming grooves or holes on the pocket surface of the cage as in Patent Document 1, and roughening the pocket surface of the cage as in Patent Document 2. These aim 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 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 Patent Document 2, the arithmetic surface roughness Ra of the pocket surface of the cage that comes into contact with the rolling elements is set to 6 μm to 10 μm, and the lubricant is held in the recesses to form a sufficient oil film. However, this parameter alone is insufficient to limit the area of ​​contact with the mating surface to a small value.

[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 specifying the surface roughness of the pocket surface using a plurality of roughness parameters, thereby enabling an oil film to be maintained on the contact surface with even a small amount of lubricant, and a rolling bearing that uses said retainer. [Means for solving the problem]

[0009] The retainer for a rolling bearing of the present invention is a resin retainer for a rolling bearing, the retainer having a plurality of pockets for holding rolling elements, characterized in that the arithmetic mean roughness Ra obtained from a roughness curve of the surface roughness of the pocket surfaces that come into contact with the rolling elements in the pockets is 3.00 μm or more and 10.00 μm or less, the average element length RSm is 0.10 mm or more and 0.40 mm or less, and the kurtosis Rku is 1.0 or more and 5.0 or less.

[0010] In one embodiment, the above-mentioned retainer is characterized in that, when any one or more (for example, all) pockets are measured in the portion of the pocket surface that comes into sliding contact with the rolling element so that the measurement direction of the roughness curve is perpendicular to the rotation direction of the rolling element, the roughness parameters obtained from the roughness curve based on JIS B 0601 have an arithmetic mean roughness Ra of 3.00 μm or more and 10.00 μm or less, an average element length RSm of 0.10 mm or more and 0.40 mm or less, and a kurtosis Rku of 1.0 or more and 5.0 or less, for all the measured pockets or their average values. Specifically, on the pocket surface of any one or more (for example, all) pockets, a point where the rolling elements and the pocket surface of 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 roughness parameters obtained from a roughness curve based on JIS B 0601 are characterized in that, for all pocket surface values ​​or their average values, the arithmetic mean roughness Ra is 3.00 μm or more and 10.00 μm or less, the average element length RSm is 0.10 mm or more and 0.40 mm or less, and the kurtosis Rku is 1.0 or more and 5.0 or less.

[0011] The pocket surface has a skewness Rsk of -1.00 or more and 1.00 or less, the skewness Rsk being calculated from a roughness curve of the pocket surface.

[0012] It is characterized in that the kurtosis Rku is greater than 3.0 and less than or equal to 5.0.

[0013] The cage is characterized in that it is an injection-molded article made of a resin composition.

[0014] 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 retainer of the present invention.

[0015] 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

[0016] The cage for a rolling bearing of the present invention has a rough surface on the pocket surface that contacts the rolling elements, and the rough surface is defined by a plurality of roughness parameters obtained from a roughness curve. Specifically, by setting the arithmetic mean roughness Ra to 3.00 μm or more and 10.00 μm or less, it becomes easy to hold the lubricant, and an oil film can be maintained on the contact surface even when the amount of lubricant supplied is small. In addition, by setting the mean length RSm of the elements to 0.10 mm or more and 0.40 mm or less, and the kurtosis Rku to 1.0 or more and 5.0 or less, the contact area with the mating surface becomes small, 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.

[0017] Furthermore, since the skewness Rsk is -1.00 or more and 1.00 or less, the bias in the height distribution is suppressed, making it easier to maintain the contact area with the counter surface small, which further contributes to suppressing the friction coefficient and temperature rise.

[0018] In addition, since the kurtosis Rku is greater than 3.0 and not greater than 5.0, the flat portions of the peaks and valleys of the roughness curve are reduced, making it possible to make the contact area with the counter surface smaller.

[0019] 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]

[0020] [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 locations of roughness parameters of the cage for a rolling bearing of the present invention. [Figure 4] FIG. 2 is a diagram for explaining the arithmetic mean roughness Ra. [Diagram 5] FIG. 13 is a diagram for explaining an average element length RSm. [Figure 6] FIG. 13 is a diagram for explaining kurtosis Rku. [Figure 7] FIG. 13 is a diagram for explaining skewness Rsk. [Figure 8] FIG. 4 is a partially enlarged perspective view showing another example of the cage for a rolling bearing of the present invention. [Figure 9] FIG. 1 is a diagram showing an outline of a Savin type friction and wear tester. [Figure 10] 1 is a graph showing the change in friction coefficient over time in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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 pocket surface 6a of the cage 5 that comes into contact with the balls in the pocket 6 is a rough surface defined by a plurality of roughness parameters. Note that this rough surface may be formed, for example, by transfer from a mold, or may be formed by machining such as shot blasting after molding.

[0026] In the present invention, the roughness parameters of the pocket surface 6a are arithmetic mean roughness Ra of 3.00 μm or more and 10.00 μm or less, mean element length RSm of 0.10 mm or more and 0.40 mm or less, and kurtosis Rku of 1.0 or more and 5.0 or less.

[0027] The pocket surface 6a for which the above-mentioned roughness parameters are defined will be specifically described with reference to FIG. 3. The pocket 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 pocket surface 6a is measured so that the measurement direction of the roughness curve is perpendicular to the rolling element rotation direction in the portion of the pocket surface 6a that comes into sliding contact with the balls 4, the roughness parameters obtained from the roughness curve based on JIS B 0601 satisfy the above-mentioned range. More specifically, when the pocket surface 6a is measured at any point within a range of ±30° (region R in FIG. 3) with one point at which the balls 4 and the pocket surface 6a may come into contact during bearing rotation (the revolution direction (X direction) of the balls 4 in FIG. 3) and a point 180° away from the one point as the center point (0°) of the measurement range, it is preferable that the roughness parameters obtained from the roughness curve based on JIS B 0601 satisfy the above-mentioned range. For example, it is preferable that the values ​​of all the pocket surfaces or their average values ​​satisfy the above-mentioned roughness parameters.

[0028] Although Figure 3 describes the pocket surface 6a of one pocket, it is sufficient that the pocket surface 6a of at least one pocket in the cage has the above-mentioned roughness parameters. For example, the pocket 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 cage) may have the above-mentioned roughness parameters, or the pocket surfaces of all pockets in the cage may have the above-mentioned roughness parameters.

[0029] Each roughness parameter will be explained below.

[0030] [Arithmetic mean roughness Ra] The arithmetic mean roughness Ra is the average absolute value of Z(x) over a reference length when the roughness curve is expressed as Z(x). Because Ra is an average value, it is not easily affected by local scratches on the surface or dirt adhering to the surface, and is therefore commonly used as an index of surface roughness.

[0031] As shown in Fig. 4, by increasing the surface Ra (for example, Ra 3.00 µm or more), the lubricant is held in the recesses and a sufficient oil film is easily formed, compared with a case where the surface Ra is small (for example, Ra 1.00 µm or less). The arithmetic mean roughness Ra is 3.00 µm or more and 10.00 µm or less, preferably 4.00 µm or more, and more preferably 5.00 µm or more. On the other hand, if Ra is large, it may affect the rotation accuracy, for example, during high-speed rotation, so Ra is preferably 8.00 µm or less, and may be less than 6.00 µm.

[0032] Here, the arithmetic mean roughness Ra is a parameter in the height direction of the roughness curved surface. Other parameters such as the maximum peak height Rp, the maximum valley depth Rv, and the maximum height Rt are also parameters in the height direction. These parameters in the height direction cannot determine the period of peaks and valleys, which is considered to be important for retaining a lubricant. In order to retain a lubricant on the contact surface, it is preferable that there are many peaks and valleys on the contact surface. In this regard, in the present invention, the average length RSm of the elements is defined as a parameter related to the lateral direction.

[0033] [Average element length RSm] The average element length RSm represents the average value of the element length in the reference length. As shown in Fig. 5, the element length is the length of one set of peaks and valleys. By making the surface RSm small (for example, RSm 0.40 mm or less) compared to when the surface RSm is large (for example, RSm 0.50 mm or more), the roughness period becomes shorter, and as a result, the contact area with the mating surface can be reduced.

[0034] The average length RSm of the elements is 0.10 mm or more and 0.40 mm or less, preferably 0.30 mm or less, and may be 0.20 mm or less.

[0035] Furthermore, in the present invention, from the viewpoint of contact with the counter surface, the shape of the contacting protrusions (peaks) is considered to be important, and kurtosis Rku is defined as a parameter thereof.

[0036] [KurtosisRku] Kurtosis Rku is a value that indicates the degree of sharpness of the probability density function of the roughness curve. As shown in Figure 6, when the value of kurtosis Rku is 3, the probability density function is a normal distribution. When the kurtosis Rku is greater than 3, the probability density function is sharp, and the roughness curve has sharp peaks and valleys. When the kurtosis Rku is less than 3, the probability density function is flat, and the peaks and valleys of the roughness curve are flat. Here, if the kurtosis Rku is too small, the peaks that come into contact with the mating surface will be flat, resulting in a contact surface that is difficult for lubricant to intervene, and the friction coefficient and temperature will be easily increased. Conversely, if the kurtosis Rku is too large, the area of ​​contact with the mating surface will be too small, and stress concentration will cause early wear and flattening.

[0037] The kurtosis Rku is 1.0 or more and 5.0 or less, and the closer the kurtosis Rku is to 3, the better the balance is, and the more easily the lubricant will be interposed between the surface. Preferably, the kurtosis Rku is more than 3.0 and 5.0 or less. This increases the sharpness of the peaks, and the contact area with the counter surface can be reduced.

[0038] In addition, other roughness parameters may be set for the roughness of the pocket surface. For example, skewness Rsk may be adopted from the viewpoint of controlling the shape of the contacting convex portion (ridge portion).

[0039] [Skewness Rsk] The skewness Rsk is a value indicating the degree of asymmetry of the probability density function of the roughness curve. As shown in FIG. 7, when the value of the skewness Rsk is 0, the height distribution is symmetrical up and down. The smaller the skewness Rsk is from 0, the more the roughness curve is biased upward from the average line, resulting in a shape with many valleys. In addition, in a shape with many valleys, the proportion of flat parts that come into contact with the counter surface tends to increase, and as a result, it becomes difficult for the lubricant to be interposed in the flat parts. Therefore, the skewness Rsk is preferably -1.0 or more. In this case, it is easier to suppress the increase in the friction coefficient and temperature. As a more preferable range, the skewness Rsk is -1.0 or more and 1.0 or less, and may be -1.0 or more and less than 0.

[0040] The above-mentioned various roughness parameters (Ra, RSm, Rku, Rsk) are values ​​calculated in accordance with JIS B 0601, and are calculated from data measured by, for example, a contact-type surface roughness measuring instrument. Specific measurement conditions for Ra are a measurement length of 12.5 mm and a cutoff of 2.5 mm.

[0041] As described above, in the cage of the present invention, the roughness of the pocket surface with which the balls contact is specified in combination with the arithmetic mean roughness Ra, a parameter related to the lateral direction (RSm), and a parameter related to the shape of the contacting ridge portion (Rku), making it possible to maintain a low friction state even under severe lubrication conditions, as will be shown in the examples described later.

[0042] In the pocket, it is sufficient that the pocket surface (see FIG. 3, for example) with which the balls come into contact has the above-mentioned roughness, and the entire pocket 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 mm2 / s or more 30mm 2 / s or less is preferred.

[0047] 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.

[0048] 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. 8. Fig. 8 is a partially enlarged perspective view of the crown type cage. As shown in Fig. 8, 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 an annular cage body, the opposing retaining claws 9 are curved in a direction approaching each other, and pockets 10 for holding balls as rolling elements are formed between the retaining claws 9. In addition, a flat portion 11 serving as a rising reference surface for the retaining claws 9 is formed between the back faces of the adjacent retaining claws 9 in the adjacent pockets 10. In the crown type cage 8, the surface roughness of the pocket surface 10a that comes into contact with the balls in the pockets 10 also has the above-mentioned multiple roughness parameters, and the contents described with reference to Fig. 3 can also be applied to this cage 8.

[0049] 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. EXAMPLES

[0050] Examples of the present invention will be described below. Using a Savin type abrasion tester shown in Fig. 9, the friction coefficients of test pieces having different surface roughnesses were evaluated.

[0051] (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 file processing to obtain the test specimens of Examples 1 and 2 and Comparative Example 1, respectively.

[0052] (2) Measurement of roughness parameters The roughness parameters (Ra, RSm, Rku, Rsk) of the sliding surface of each test piece obtained above were measured by a stylus surface roughness tester. Each roughness parameter is a value calculated in accordance with JIS B 0601, and is measured using a contact or non-contact surface roughness meter. Specific measurement conditions are a cutoff value λc = 0.8 mm or λc = 2.5 mm, and a reference length equal to the cutoff value is defined as one section, and the average value of five sections is taken as the measured value. The cutoff value varies depending on the surface roughness, and is a value determined based on JIS B 0601. The measurement results are shown in Table 1 below. The surface roughness of Comparative Example 1 is equivalent to the roughness of a cage obtained by general injection molding.

[0053] When measuring the roughness of a cage, for example, 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 rolling elements and cage pocket surface 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° is measured.

[0054] [Table 1]

[0055] (3) Saban type abrasion test A Savin type wear tester 21 shown in FIG. 9 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 more 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. <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)

[0056] The change in the coefficient of friction over time in the Savin wear test is shown in Fig. 10. As shown in Fig. 10, compared to Comparative Example 1, Examples 1 and 2 had lower coefficients of friction during the test and smaller variations in the coefficients of friction. Specifically, the coefficients of friction in Examples 1 and 2 remained below 0.3 until 20 hours had elapsed from the start of the test. In this way, when the contact surface has the surface roughness defined in the present invention, it is possible to reduce the coefficient of friction during sliding.

[0057] Furthermore, compared to Example 1, Example 2 had a smaller friction coefficient value, and the friction coefficient of Example 2 was less than 0.2 until 20 hours had passed from the start of the test. For example, Example 2 had a larger arithmetic mean roughness Ra than Example 1, and this difference is thought to have influenced the experimental results. For example, by setting Ra to 5.00 μm or more, it is expected that friction will be further reduced. [Industrial Applicability]

[0058] The retainer for a rolling bearing of the present invention defines the surface roughness of the pocket surface using multiple roughness parameters, allowing an oil film to be maintained on the contact surface even with 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]

[0059] 1 Angular contact ball bearings (rolling bearings) 2. Inner Circle 3 Outer ring 4 balls (rolling elements) 5 Cage 6 Pockets 6a Pocket side 7 Pillar part 8 Cage 9 retaining claw 10 Pocket 10a Pocket 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, The retainer has a plurality of pockets for holding rolling elements, and is characterized in that the arithmetic mean roughness Ra calculated from a roughness curve of the surface roughness of the pocket surfaces that come into contact with the rolling elements in the pockets is 3.00 μm or more and 10.00 μm or less, the average element length RSm is 0.10 mm or more and 0.40 mm or less, and the kurtosis Rku is 1.0 or more and 5.0 or less.

2. 2. The cage for a rolling bearing according to claim 1, wherein a skewness Rsk determined from a roughness curve of the pocket surface is in the range of -1.00 to 1.

00.

3. 3. The cage for a rolling bearing according to claim 1, wherein the kurtosis Rku is greater than 3.0 and not greater than 5.

0.

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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