Retainer for rolling bearing, and rolling bearing

Abstract

This rolling bearing comprises an annular retainer (1A) for rotatably holding a rolling element such as a roller (4). The retainer (1A) is provided such that: the arithmetic average roughness (Ra) of one or more retainer surfaces selected from an outer diameter surface (1a), an inner diameter surface (1b), and a width surface (1c) of the retainer (1A), and an inner surface (5a) of a rolling element holding pocket (5) penetrating in the radial direction is 2 μm ≤ Ra ≤ 20 μm; and the root mean square inclination (RΔq) of a roughness curve of the retainer surface is 10° ≤ RΔq ≤ 40°.

Description

Rolling bearing retainer and rolling bearing

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

[0002] Generally, rolling bearings are sometimes used without a sufficient supply of lubricating oil, for example, rolling bearings incorporated into reduction mechanisms and transmission mechanisms such as e-axles, automatic transmissions (ATs), and continuously variable transmissions (CVTs), which combine the main components such as gears and motors required for automobiles powered by motors, do not receive a supply of lubricating oil when the automobile is stopped.In such cases, the lubricating oil adhering to the rolling bearings drips from the rolling bearings and flows out to the bottom of the device.

[0003] If the vehicle is restarted in such a state where there is insufficient supply of lubricating oil, the rolling bearings may rotate at high speed without sufficient lubricating oil reaching them, and even in such cases it is necessary to prevent the rolling bearings from seizing.

[0004] In addition, in recent years, automobiles have tended to use smaller amounts of low-viscosity lubricating oil due to the drive to reduce fuel consumption and electricity consumption, and rolling bearings are now being used under conditions that make them more susceptible to temperature increases and seizure than before.

[0005] It is known to provide a lubricating coating made of a self-lubricating resin or metal on the surface of the cage or the like so that rolling bearings can fully demonstrate their rotational performance and durability under more severe than normal operating conditions, including not only automobiles but also aircraft.

[0006] However, self-lubricating coatings tend to peel off easily from the substrate and are prone to wear, so further improvements are required to ensure that rolling bearings can maintain stable rotational function and durability even under harsh operating conditions.

[0007] For example, as a rolling bearing that can rotate at high speeds over time (for a period of from several tens of seconds to several tens of minutes) even under severe conditions of use in which the supply of lubricating oil to the rolling bearing is cut off and only a very small amount of initially adhered oil is present, that is, a so-called "dry run" condition, there is known a rolling bearing for aircraft in which the surface roughness Ra of the inner diameter surface, outer diameter surface, or pocket portion for retaining the rolling elements is specified to be 0.8 to 6.5 μm (Patent Document 1).

[0008] JP 2012-180847 A

[0009] However, in the above-mentioned rolling bearings for aircraft, the surface roughness of the inner diameter surface, outer diameter surface or pocket portion of the annular cage is specified only by the parameter Ra, which is the average of the absolute values ​​of the peaks and valleys from the mean plane of the roughness curve, and therefore the surface properties of such cages that can retain the extremely small amount of initially adhered oil have not been sufficiently specified.

[0010] Therefore, even if the surface roughness Ra of a specified guide surface, such as the inner diameter surface, outer diameter surface or pocket portion of the annular retainer, is 0.8 to 6.5 μm, the friction coefficient of the guide surface may increase rapidly after a short period of use, and the temperature of the guide surface, its lubricating oil and parts adjacent to the retainer may rise, which may interfere with normal and stable rotation of the rolling bearing.

[0011] Therefore, the object of this invention is to solve the above-mentioned problems by providing a cage for a rolling bearing that does not cause the temperature of the rolling bearing to rise, that maintains a low and stable coefficient of friction on the surfaces of the cage, such as guideways, even in conditions such as a lack of lubricating oil, and that enables the rolling bearing to maintain a normal and stable rotational state for the required time, and to create a rolling bearing that has excellent seizure resistance and wear resistance using such a cage.

[0012] In order to solve the above problems, the present invention provides a cage for a rolling bearing, which is an annular cage that rotatably holds the rolling elements of a rolling bearing, the annular cage having holes that penetrate in the radial direction, the holes being pockets that hold the rolling elements, the arithmetic mean roughness (Ra) of one or more cage surfaces selected from the inner surface of this pocket, the outer diameter surface, the inner diameter surface and the width surface of the cage being 2 μm≦Ra≦20 μm, and the root mean square slope (RΔq) of the roughness curve of the cage surface being 10°≦RΔq≦40°.

[0013] In this invention, the width surface refers to the end surface in the axial direction of the annular cage. The reason why the object to be specified using parameters related to surface roughness in this invention is "one or more cage surfaces" is that the guide type of the cage includes raceway guide (inner ring guide or outer ring guide) and rolling element guide, the optimum guide type (guide surface) is selected depending on the application of the rolling bearing, and the guide surface may change depending on the conditions of use, etc., so the object of the cage surface to be specified is not limited to one location.

[0014] The rolling bearing retainer of the present invention configured as described above has an arithmetic mean roughness (Ra) on the retainer surface that is 2 μm≦Ra≦20 μm, and therefore has minute irregularities with an appropriate height difference, which allows the retainer surface to retain as much lubricant as possible.

[0015] Furthermore, since the root mean square slope (RΔq) of the roughness curve of the cage surface is 10°≦RΔq≦40°, the slope angle of the peaks of minute irregularities is optimized, and the lubricant held on the cage surface is efficiently and continuously transferred to and lubricates the required surfaces of one or more components, such as rolling elements, that are in constant or intermittent contact with the cage. In addition, the tip shape of the roughness protrusions (peaks) becomes sharp, reducing the actual contact area with the rolling elements or components and ensuring the minimum appropriate area required.

[0016] In addition to the rolling elements, examples of parts that are in constant or intermittent contact with the surface of the retainer include inner members such as the inner ring of a rolling bearing or the shaft in a planetary gear mechanism, outer members such as the outer ring of a rolling bearing or the pinion gear in the planetary gear mechanism, and washers installed close to the width face of the retainer.

[0017] Therefore, even when the rolling bearing is used in a state where the supply of lubricating oil from outside is cut off or insufficient, the temperature of the surface of the rolling bearing and adjacent parts does not rise, and the rolling bearing can maintain a normal and stable rotation state for the required time.Using such a retainer, a rolling bearing with excellent seizure resistance and wear resistance can be obtained.

[0018] In order to obtain this effect more stably, the rolling bearing cage of the present invention preferably has a root mean square roughness (Rq) of the roughness curve of the cage surface in the range of 2 μm≦Rq≦20 μm. If Rq is within this range, the variation in the size of the irregularities on the cage surface is limited to within the range, and the lubricant retained on the cage surface can be efficiently, stably, and continuously transferred to parts adjacent to the periphery of the cage.

[0019] Furthermore, it is preferable that the average height (Rc) of the roughness curve of the cage surface is 10 μm≦Rc≦70 μm. When Rc, which is the average height of the irregularities on the cage surface, is within this numerical range, a sufficient amount of lubricant can be held on the cage surface, stabilizing the amount of lubricant supplied from the cage surface to parts in close proximity to the cage, and maintaining a normal and stable rotation state of the rolling bearing more stably for the required time.

[0020] A rolling bearing retainer that achieves the above-mentioned effects can be made from an appropriate synthetic resin or metal depending on the intended use of the rolling bearing, and the surface of the retainer can be prepared to the above-mentioned specified surface roughness by an existing molding method or surface treatment.

[0021] By using such a rolling bearing cage to rotatably support the rolling elements, the normal and stable rotation of the rolling bearing can be maintained for the required time, even in a dry run, for example, and a rolling bearing with excellent seizure resistance and wear resistance can be created.

[0022] This invention has the advantage that by setting the arithmetic mean roughness (Ra) and root mean square slope (RΔq) of the roughness curve of the retainer surface of a rolling bearing within the specified numerical ranges of 2 μm≦Ra≦20 μm and 10°≦RΔq≦40°, the temperature of the lubricating oil on the surface of the retainer for the rolling bearing and the parts in close proximity to the retainer do not rise, the coefficient of friction on the retainer surface remains low and stable even in a state of insufficient lubrication, and the rolling bearing can maintain a normal and stable rotation state for the required time, and furthermore, by using such a retainer, it is possible to create a rolling bearing with excellent seizure resistance and wear resistance.

[0023] Graph showing the results of measuring RΔq for Example 1 and Comparative Examples 1 and 2. Graph showing the results of measuring Ra, Rq, and Rc for Example 1 and Comparative Examples 1 and 2. Graph showing the results of a friction and wear test (in an oil-immersed state) and showing the change in friction coefficient over time for Example 1 and Comparative Examples 1 and 2. Graph showing the results of a friction and wear test (in an oil-immersed state) and showing the change in oil temperature over time for Example 1 and Comparative Examples 1 and 2. Graph showing the results of a friction and wear test (in an oil-naturally removed state) and showing the change in friction coefficient over time for Example 1. Graph showing the results of a friction and wear test (in an oil-naturally removed state) and showing the change in friction coefficient over time for Comparative Examples 1 and 2. Graph showing the results of a friction and wear test (in an oil-naturally removed state) and showing the change in friction coefficient over time for Example 1.

[0024] The rolling bearing cage of the present invention and the rolling bearing using the same will be described in detail below with reference to the accompanying drawings.

[0025] As shown in Figures 1 to 3, the synthetic resin cage 1A for a rolling bearing of the first embodiment is an annular (substantially cylindrical) cage 1A that rotatably holds the rollers 4 (Figure 1) of a rolling bearing (cage 1A and rollers 4) that supports a pinion gear (planetary gear) 3 incorporated in a planetary gear mechanism 2 (Figure 3), and is a rolling bearing cage that is adjusted so that the arithmetic mean roughness (Ra) of one or more cage surfaces selected from the inner surface (pillar portion) 5a and inner surface (end portion) 5b of a rolling element holding pocket 5 that penetrates radially through the annular shape, and the outer diameter surface 1a, inner diameter surface 1b, and width surface 1c of the cage 1A is 2 μm≦Ra≦20 μm, and the root mean square slope (RΔq) of the roughness curve of the cage surface is 10°≦RΔq≦40°.

[0026] As shown in FIG. 3 , the planetary gear mechanism 2 includes a ring gear 6 having internal teeth surrounding the outer periphery, a sun gear (sun gear) 7 having external teeth and disposed at the center of the ring gear 6, and a plurality of pinion gears 3 having external teeth and disposed between the ring gear 6 and the sun gear 7.

[0027] Each pinion gear 3 meshes with a ring gear 6 and a sun gear 7, and the pinion shaft 8, which is an engaging shaft, is supported by the pinion gear 3 and rollers 4 rotatably held by a cage 1A. The end of the pinion shaft 8 is connected to a carrier 9 (FIG. 1), and the rotational force required for the revolution of the planetary gears is input and output from this carrier 9 to drive the planetary gear mechanism 2. In this planetary gear mechanism 2, the inner diameter surface 3a of the pinion gear 3 corresponds to the inner circumferential surface of the outer ring of the rolling bearing, and the outer circumferential surface 8a of the pinion shaft 8 corresponds to the outer circumferential surface of the inner ring of the rolling bearing.

[0028] Furthermore, an oil passage hole 10 is formed inside the pinion shaft 8 for supplying lubricating oil, and the lubricating oil is guided through the oil passage hole 10 to the outer peripheral surface 8a of the pinion shaft 8, the inner diameter surface 3a of the pinion gear 3, the rollers 4, the inner diameter surfaces (pillar portions) 5a and (end portions) 5b of the rolling element holding pockets 5, the outer diameter surface 1a and inner diameter surface 1b of the cage, and the width surfaces 1c which are the axial end surfaces, thereby lubricating these rolling bearing parts. It goes without saying that the inner diameter surfaces (pillar portions) 5a of the rolling element holding pockets 5 include the surfaces of the outer and inner claws which restrict the rollers 4 from moving radially outward or inward.

[0029] Such a synthetic resin retainer 1A is prepared so that one or more predetermined surfaces selected from the inner surface (column portion) 5a and inner surface (end portion) 5b of the rolling element retaining pocket 5, the outer diameter surface 1a, inner diameter surface 1b, and width surface 1c of the retainer 1A are within the predetermined numerical ranges of the above-mentioned predetermined surface roughness parameters Ra and RΔq, and further so that Rq and Rc, which will be described later, are within predetermined numerical ranges, and for this preparation, ordinary resin molding techniques such as injection molding and surface treatment techniques are used.

[0030] That is, for example, by finishing the surface roughness of a mold used in injection molding or the like in advance by the following surface treatment so that it falls within the numerical range of the above-mentioned predetermined roughness parameters, it is possible to manufacture a rolling bearing cage with the above-mentioned predetermined surface properties.

[0031] Specifically, when machining a mold, die-sinking electrical discharge machining is performed to transfer the shape of the electrode onto the workpiece. The electrode used in this process is finished to the desired roughness by surface treatment such as machining, shot blasting, or etching, and then this electrode is used to electrical discharge machine the surface of the mold.

[0032] In addition to the roughness of the electrode, the required surface roughness can be adjusted by adjusting the swing of the electrode during electrical discharge machining (amount of electrode movement), the gap between the machining surface and the electrode (gap, generally a discharge gap of 0.005 to 1.0 mm), and the discharge energy. Furthermore, instead of adjusting the roughness of the electrode, the roughness of the injection molding die itself may be finished by blasting treatment such as sandblasting or shot blasting, etching treatment such as chemical etching or electrolytic etching, or machining. For example, in the case of chemical etching, the required surface roughness can be adjusted by adjusting the type and concentration of the etching solution and the chemical reaction time (corrosion time).

[0033] As for the type of synthetic resin used for the retainer material, it is preferable to use a thermoplastic resin from the standpoint of adjusting the surface properties and manufacturing efficiency, but any appropriate resin can be used without any particular restrictions depending on the characteristics required of the rolling bearing.

[0034] For example, polyamide (PA) resin is a thermoplastic resin that has excellent heat resistance and can be melt-molded. By using PA10T (melting point 315°C) or PA9T (melting point 300°C), the desired performance of the retainer can be fully achieved even when the bearing is exposed to a high-temperature environment.

[0035] It is preferable that the thermoplastic resin contains a reinforcing material to improve strength, and in addition to fibrous reinforcing materials such as glass fiber and carbon fiber, well-known reinforcing materials can be used.

[0036] PA10T is a resin material made from biomass-derived raw materials (e.g., about 37% biomass content), which contributes to carbon neutrality and has few constraints in terms of manufacturing costs. One commercially available product of PA10T is XecoT XG510A30D, manufactured by Unitika Ltd., which contains about 30% glass fiber.

[0037] Although the melting point of PA9T is lower than that of PA10T, it is higher than other PA resins, and it is expected to have the same heat resistance as PA10T. As a commercially available PA9T product, GENESTAR G1300A manufactured by Kuraray Co., Ltd., which contains about 30% glass fiber, can be used.

[0038] Next, a metal cage 1B for a rolling bearing according to a second embodiment shown in FIG. 4 can, like the synthetic resin cage 1A described above, be incorporated into a planetary gear mechanism 2 (FIG. 3) and can rotatably hold rollers (not shown) of a rolling bearing that can support a pinion gear 3.

[0039] Such a metal cage is manufactured by, for example, using SPCC-SD, a cold-rolled steel plate finished to a dull finish (matt finish), finishing the rolling roll surface during cold rolling to a surface having the roughness required for this invention, cold rolling with this roll to form coil material, and pressing this coil material.

[0040] In addition, after a commercially available cold-rolled steel plate such as SPCC-SD is pressed to produce a retainer, the outer diameter surface, inner diameter surface, guide surfaces and width surfaces of the pocket portion of the retainer may be subjected to blasting, etching or machining to finish the surface to have the roughness required for this invention.

[0041] In other words, even in the case of an annular retainer made of metal rather than synthetic resin, the surface roughness of the retainer guide surfaces or width surfaces 1f selected from the inner surface (pillar portion) 11a, inner surface (end portion) 11b of the pocket 11 that radially penetrates the retainer 1B, and the outer diameter surface 1d and inner diameter surface 1e of the retainer 1B can be adjusted to the required roughness by pressing coil material that has been cold-rolled with a rolling roll having the required roughness described above, or by subjecting the retainer manufactured by pressing to blasting, etching or machining.

[0042] In the first and second embodiments, the inner surface 5b ( FIG. 2 ) or 11b ( FIG. 4 ) is a portion that may come into contact with the end face of the roller 4, and the width surface 1c or 1f is a portion that may come into contact with the washer 12, which is a fixed component in the width direction. In other words, when a rolling bearing is used in such a situation where the rotation axis of the roller is not parallel to the central axis (called skew), a phenomenon known as lateral movement occurs, in which the rollers or cage move axially. In this case, an axial load (induced axial load) is generated in the bearing, and wear and other damage may occur on the inner surface 5b or 11b, which is likely to come into contact with the rollers, and on the width surface 1c or 1f, which is likely to come into contact with fixed components such as the washer 12. For these reasons, it is effective to set the surface roughness of the inner surface 5b or 11b and the width surface 1c or 1f within the specified numerical ranges described in this invention.

[0043] As described above, the roughness parameters required for a specified surface of the cage common to the first and second embodiments are an arithmetic mean roughness (Ra) of 2 μm≦Ra≦20 μm, and a root mean square slope (RΔq) of the roughness curve of the cage surface of 10°≦RΔq≦40°.

[0044] Furthermore, it is preferable that the root mean square roughness (Rq) of the roughness curve of the cage surface is 2 μm≦Rq≦20 μm, and in addition, the mean height (Rc) of the roughness curve is 10 μm≦Rc≦70 μm.

[0045] The surface roughness parameter Ra is the average value of the height difference from the average surface of the contour shape, and is a parameter that is less susceptible to disturbances such as scratches, dust, and noise, and can provide stable results.

[0046] Rq is a roughness parameter obtained by squaring the unevenness variation relative to a reference surface, calculating the average value, and then taking the square root, and is sometimes called the RMS value. By squaring the unevenness variation, Rq emphasizes high convexities, and the value increases when there are large unevenness, so it is suitable for evaluation taking into account both average variation and large unevenness.

[0047] If Ra and Rq are smaller than 2 μm, it becomes difficult for lubricating oil to flow into or out of the gap between the retainer surface and the raceway surface or the rolling surface, or the gap between the retainer surface (width surface) and the fixed parts in the width direction, and if a condition is added that causes RΔq to fall outside the specified numerical range described below, it becomes difficult to improve seizure resistance and reduce the friction coefficient and temperature rise.

[0048] If Ra and Rq are greater than 20 μm, the dimensional variation of the finished cage unit will increase, making it difficult to ensure the dimensions and shape precision (roundness, cylindricity, etc.), and making it difficult to set the desired guide clearance (the clearance between the cage and the raceway ring or rolling elements). In addition, if the contact state with the bearing raceway surface becomes uneven and conditions are added where RΔq falls outside the specified numerical range described below, the friction coefficient and bearing temperature may increase, and the life of the rolling bearing may also be shorter than expected.

[0049] RΔq (also called Δq or Rdq) represents the root mean square of the local slope of the roughness curve, and is a parameter that evaluates the magnitude of the local slope angle. It is a numerical representation of the steepness of the surface irregularities, and the larger the value of RΔq, the larger the slope angle of the local part (peak) of the profile curve.

[0050] By setting RΔq within the range of 10°≦RΔq≦40°, it is possible to optimize the roughness profile (local inclination angle) of the retainer surface that comes into contact with the mating surface (bearing raceway surface, rolling surface, or width surface of a fixed component in the width direction), and it is possible to efficiently and continuously transfer the lubricant held on the retainer surface to one or more of the mating surfaces, namely the inner ring (inner member), outer ring (outer member), and rolling elements or the fixed component in the width direction.

[0051] If RΔq is less than 10°, it becomes difficult for lubricating oil to flow in and out of the bearing between the mating surface, making it difficult to improve seizure resistance, reduce the coefficient of friction, and reduce bearing temperature rise. If RΔq is greater than 40°, the contact area between the tips of the convex portions on the cage surface and the mating part becomes smaller, making it easier for wear and deformation of the tips of the convex portions to progress due to contact with the mating surface, which is undesirable. For these reasons, RΔq is more preferably 10°≦RΔq≦30°, and even more preferably 15°≦RΔq≦25°.

[0052] Rc is a parameter that represents the average value of the height of the profile element over the reference length. A profile element is a pair of adjacent peaks and valleys, and the average value of the difference in height between the peak and the valley bottom is the average height of the roughness profile element.

[0053] By setting the average height Rc of the roughness curve of the cage surface to 10 μm≦Rc≦70 μm, the roughness of the cage surface (irregularities in the contour shape) can be controlled, and a sufficient amount of lubricant can be stably retained on the cage surface. If Rc is less than 10 μm, it becomes difficult for lubricant to flow into and out of the gaps between the cage surface and the raceway surfaces or rolling surfaces, or between the cage surface (width surface) and fixed parts in the width direction, and if conditions are added that result in RΔq being outside the specified numerical range described below, it becomes difficult to improve seizure resistance and reduce the friction coefficient.

[0054] Furthermore, if Rc is greater than 70 μm, the dimensional variation of the finished cage unit increases, making it difficult to ensure the dimensions and shape precision (roundness, cylindricity, etc.), and it becomes difficult to set the desired guide clearance (the clearance between the cage and the raceway rings or rolling elements).In addition, the contact state with the bearing raceway surface becomes uneven, and if conditions are added where RΔq, described below, is outside the specified numerical range, this can lead to an increase in the friction coefficient and temperature and a shortened bearing life.

[0055] The type of rolling bearing in the first and second embodiments described above is exemplified as a needle bearing (needle roller bearing), but is not limited to this and may be a cylindrical roller bearing, a tapered roller bearing, a self-aligning roller bearing, a ball bearing, etc.

[0056] Example 1 A polyamide resin (PA10T) containing 30% glass fiber (XecoT XG510A30D, manufactured by Unitika Ltd.) was used as the molding material for the resin cage, and injection molding was performed using an embossing mold (a mold with surface roughness of approximately RΔq 19°, Ra 7 μm, Rq 9 μm, and Rc 27 μm) to mold a resin cage in the form shown in FIG. 2 , in which the inner surfaces of the rolling element holding pockets and the outer and inner diameter surfaces of the cage were formed with embossed surfaces having the above-mentioned roughness.

[0057] Furthermore, three plate-shaped test pieces (40 mm x 40 mm) 13 shown in Figure 5 were prepared using a test piece molding die having a textured surface with the same surface roughness as the textured die.

[0058] The surface roughness parameters RΔq, Ra, Rq, and Rc of each test piece were measured using a surface roughness measuring instrument. RΔq, Ra, Rq, and Rc are parameters specified in JIS B0601:2013, and the measurement conditions were as follows: a measurement length of 15 mm in the XY direction, an evaluation length of 12.5 mm, and a cutoff λ of 1.0 mm at any two points on the surface of each test piece. Ｃ 2.5 mm, λ ｓ The measurements were made at 0.008 mm, and the average values ​​were calculated, which are shown in Table 1, FIG. 6 or FIG.

[0059]

[0060] Comparative Example 1 A resin cage was molded in exactly the same manner as in Example 1, except that a normal mold (with a smooth surface) was used instead of a texture mold, and three plate-shaped test pieces (40 mm × 40 mm) 13 shown in Fig. 5 were prepared using a test piece molding mold also having a smooth surface. For each test piece, the surface roughness parameters RΔq, Ra, Rq, and Rc were measured in the same manner as in Example 1, and the results are shown in Table 1, Fig. 6, or Fig. 7.

[0061] Comparative Example 2 Using SPCC cold-rolled steel sheet as the forming material for the metal cage, the cold-rolled steel sheet was used with rolls having a dull finish, which is the rolling roll surface typically used during cold rolling, to form a coil material, and this coil material was press-formed to form the rolling bearing cage shown in Fig. 4, and three plate-shaped test pieces (40 mm x 40 mm) 13 shown in Fig. 5 were also prepared. For each test piece, the surface roughness parameters RΔq, Ra, Rq, and Rc were measured in the same manner as in Example 1, and the results are shown in Table 1 and Fig. 6 or 7.

[0062] Next, the test pieces of Example 1 and Comparative Examples 1 and 2 obtained as described above were subjected to the following friction and wear tests 1 and 2.

[0063] <Friction and Wear Test 1 (Oil Immersion Condition) In accordance with JIS K7218 Method A, test pieces 13 of Example 1 and Comparative Examples 1 and 2 were immersed in lubricating oil as shown in Figure 5, and test pieces 13 were rotated while a load of 150 N (surface pressure at the contact point between cylindrical jig 14 and test piece 13: 0.75 MPa) was applied using a metal cylindrical jig 14, and the changes in friction coefficient and oil temperature over time were measured under the following conditions: test (relative) speed of the sliding surface: 1.5 m / s, sliding distance: 9000 m, PV value: 1125 kPa m / s. Note that the test speed and sliding distance were three times the conditions specified in the JIS method.

[0064] The oil used was a hydraulic oil for hybrid vehicles, with a kinematic viscosity of 11.8 cSt (40°C) and 3.3 cSt (100°C).These results are shown in Figures 8 and 9.

[0065] <Friction and Wear Test 2 (Naturally Removed Oil State)> The changes in the friction coefficient and the cylindrical jig temperature over time were measured in exactly the same manner as in Friction and Wear Test 1, except that test pieces 13 of Example 1 and Comparative Examples 1 and 2 in a naturally removed oil state were used, and the results are shown in Figure 10, Figure 11, or Figure 12. Note that the "naturally removed oil state" refers to a state in which a plate-shaped test piece was immersed in oil at room temperature, then removed from the oil, and left to stand for 24 hours with the plate surface approximately vertical, and Friction and Wear Test 2 was then carried out in this state without lubrication.

[0066] The metallic cylindrical jig 14 was made of S45C material, and in both friction and wear tests 1 and 2, the contact surface with the test piece was polished with #2000 before each test.

[0067] From the results of the surface roughness measurements and the friction and wear tests 1 and 2 for Example 1 and Comparative Examples 1 and 2, the following evaluations can be made.

[0068] As shown in Figures 6 to 12, Example 1, in which the surface roughness parameters of the test specimens were Ra 2 μm or more and RΔq 10° or more, showed less change in the friction coefficient over time in the friction and wear test in both the oil-immersed state (Figure 8) and the naturally oil-removed state (Figure 10) compared to Comparative Examples 1 and 2, and the oil temperature during the test was low and stable at around 33°C or less (Figure 9). The cylindrical jig temperature in the naturally oil-removed state of Example 1 (Figure 12) was stable at around 60-70°C for about 10-15 minutes after the start of the test, but rose sharply to around 200°C after 10-15 minutes, presumably because the oil retained on the surface of the test specimen was removed by splashing. However, the cylindrical jig temperature in Example 1 was lower than that of Comparative Examples 1 and 2, and the specimen did not melt.

[0069] On the other hand, the test pieces of Comparative Examples 1 and 2, in which the surface roughness parameters of the test pieces were Ra less than 2 μm and RΔq less than 10°, had friction coefficients that became unstable and rose significantly within about 1 to 2 minutes even when immersed in oil ( FIG. 8 ), and the oil temperature also rose to about 35 to 45°C after 30 minutes ( FIG. 9 ), and further rose to 40 to 50°C after 100 minutes.

[0070] In particular, the friction coefficient of the test piece of Comparative Example 1 fluctuated significantly and became unstable within 2 to 3 minutes after natural oil removal, and the resin test piece melted in about 10 minutes.

[0071] In addition, the friction coefficient of the test piece of Comparative Example 2 also became unstable within 2 to 4 minutes, a loud metallic sound was generated, and the thermocouple became detached from the cylindrical jig, making it impossible to measure the temperature. The temperature of the cylindrical jig of the test piece whose thermocouple did not come off rose to a high temperature exceeding 200°C within a few minutes.

[0072] From these results, it was found that only the test specimen of Example 1 had a low and stable friction coefficient of the sliding friction surface even under high-speed sliding conditions where it was lubricated with an insufficient amount of lubricant or a lubricant with a relatively low viscosity, and when used as a cage for a rolling bearing, it was possible to minimize the rotational torque and heat generation of the bearing.

[0073] The present invention can be widely used industrially, for example, as a rolling bearing lubricated with an insufficient amount of lubricant or a low-viscosity lubricant, such as a rolling bearing incorporated into a reduction mechanism or a transmission mechanism of an automobile e-axle, automatic transmission (AT), continuously variable transmission (CVT), or the like, a rolling bearing that rotates at high speed, or a retainer for a rolling bearing that requires that the rotational torque and heat generation of the bearing be minimized, or a rolling bearing equipped with such a retainer.

[0074] DESCRIPTION OF SYMBOLS 1A, 1B Cage 1a, 1d Outer diameter surface 1b, 1e Inner diameter surface 1c, 1f Width surface 2 Planetary gear mechanism 3 Pinion gear 3a Inner diameter surface of pinion gear 4 Rollers 5, 11 Pocket 5a, 11a Inner surface (pillar portion) 5b, 11b Inner surface (end portion) 6 Ring gear 7 Sun gear 8 Pinion shaft 8a Outer periphery 9 Carrier 10 Oil passage hole 12 Washer 13 Test piece 14 Cylindrical jig

Claims

1. An annular cage for rotatably holding rolling elements of a rolling bearing, wherein the annular cage has holes penetrating in the radial direction, the holes are pockets for holding the rolling elements, and the arithmetic mean roughness (Ra) of one or more cage surfaces selected from the inner surface of the pockets, the outer diameter surface, the inner diameter surface, and the width surface of the cage is 2 μm ≤ Ra ≤ 20 μm, and the root mean square slope (RΔq) of the roughness curve of the cage surface is 10° ≤ RΔq ≤ 40°. A cage for a rolling bearing.

2. The cage for a rolling bearing according to claim 1, wherein the root mean square roughness (Rq) of the roughness curve of the cage surface is 2 μm ≤ Rq ≤ 20 μm.

3. The cage for a rolling bearing according to claim 1 or 2, wherein the average height (Rc) of the roughness curve of the cage surface is 10 μm ≤ Rc ≤ 70 μm.

4. The cage for a rolling bearing according to claim 1 or 2, wherein the cage is made of synthetic resin or metal.

5. The cage for a rolling bearing according to claim 3, wherein the cage is made of synthetic resin or metal.

6. A rolling bearing provided with the cage according to any one of claims 1 to 5.

7. A needle bearing provided with the cage according to any one of claims 1 to 5.

8. A planetary gear mechanism in which a planetary gear is supported by the needle bearing according to claim 7.

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