Holder for rolling bearing and rolling bearing

Abstract

To create a holder for a rolling bearing in which a coefficient of friction of a surface of a holder keeps low stably even in a lubricant shortage state without increasing a temperature of a rolling bearing, and a rotation state of the rolling bearing may be kept normal and stable for a prescribed period of time, and a rolling bearing with excellent seizure resistance and abrasion resistance using such a holder.SOLUTION: Provided are: an annular holder for a rolling bearing that rotatably holds a rolling element of a rolling bearing, where the arithmetic mean roughness (Ra) of one or more holder surfaces selected from an inner surface of a rolling element holding pocket that radially penetrates the holder, an outer diameter surface, an inner diameter surface, and a width surface of the holder is 2 μm≤Ra≤20 μm, and the root mean square slope (RΔq) of the roughness curve of the holder surface is 10°≤RΔq≤40°; and a rolling bearing using such a holder.SELECTED DRAWING: Figure 8

Description

Technical Field

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

Background Art

[0002] Generally, a rolling bearing may be used in a state where lubricating oil is not sufficiently supplied. For example, in an e-Axle that combines main components such as gears and motors required for an automobile powered by a motor, a reduction mechanism or a transmission mechanism such as an automatic transmission (AT) or a continuously variable transmission (CVT), the lubricating oil is not supplied when the automobile is stopped. At that time, the lubricating oil adhering to the rolling bearing drips from the rolling bearing to the lower part of the device and flows out.

[0003] When the automobile is restarted from such a state where the lubricating oil is not sufficiently supplied, the rolling bearing is rotated at high speed in a state where sufficient lubricating oil does not reach the rolling bearing. Even in such a case, it is necessary to prevent the rolling bearing from seizing.

[0004] In recent years, automobiles have been affected by the promotion of low fuel consumption and low power consumption, and tend to use a small amount of low-viscosity lubricating oil. Rolling bearings are used under conditions where temperature rise and seizure are more likely to occur than before.

[0005] It is known to provide a lubricating film made of a self-lubricating resin or metal on the surface of a cage or the like so that the rotational performance and durability of the rolling bearing can be fully exhibited under more severe usage conditions including not only automobiles but also aircraft.

[0006] However, since the self-lubricating film also has the properties of being easily peeled off from the material and being easily worn, further improvement is required to fully exhibit the stability and durability of the rotational function in the rolling bearing even under severe usage conditions.

[0007] For example, in a severe operating condition where the supply of lubricating oil to a rolling bearing is cut off and only a very small amount of initially adhering oil remains, that is, in a so-called "dry run" state, a rolling bearing capable of high-speed rotation for a certain period of time (about several tens of seconds to several tens of minutes) over time is known. Specifically, for an aircraft rolling bearing, the surface roughness Ra of the inner diameter surface, outer diameter surface of an annular cage, or the surface of a pocket portion for holding rolling elements is specified to be 0.8 to 6.5 μm (Patent Document 1).

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, for the above-mentioned aircraft rolling bearing, since the surface roughness of the inner diameter surface, outer diameter surface of the annular cage, or the pocket portion is specified only by Ra, which is the average of the absolute values of the peaks and valleys from the mean plane of the roughness curve, the surface properties capable of holding a very small amount of initially adhering oil in such a cage have not been sufficiently specified.

[0010] Therefore, even if the surface roughness Ra of the inner diameter surface, outer diameter surface, or pocket portion of the annular cage, which is a predetermined guide surface, is 0.8 to 6.5 μm, the friction coefficient of the guide surface may increase rapidly during short-term use, and the rotation of the normal and stable rolling bearing may be hindered by the increase in the temperature of the guide surface, its lubricating oil, and the components adjacent to the cage.

[0011] Therefore, an object of the present invention is to solve the above problems, and provide a rolling bearing cage that can maintain a normal and stable rotation state of the rolling bearing for a required time with a low and stable friction coefficient on the surface of the cage such as the guide surface without increasing the temperature of the rolling bearing, for example, even in a state of insufficient lubricating oil. Another object is to create a rolling bearing excellent in seizure resistance and wear resistance by using such a cage.

Means for Solving the Problem

[0012] In order to solve the above problems, the present invention provides an annular cage for rotatably holding rolling elements of a rolling bearing. The annular cage has holes penetrating in the radial direction, and the holes are pockets for holding the rolling elements. The arithmetic mean roughness (Ra) of one or more cage surfaces selected from the inner surface of the pocket, 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°. Thus, it is a cage for a rolling bearing.

[0013] Note that the width surface referred to in the present invention is the end surface of the annular cage in the axial direction. Also, the reason why the object specified using the parameters related to the surface roughness in the present invention is "one or more cage surfaces" is that the guiding forms of the cage include raceway guiding (inner race guiding or outer race guiding) and rolling element guiding, and an optimal guiding form (guiding surface) is selected according to the use of the rolling bearing, and the guiding surface may change depending on the use conditions, etc. The cage surfaces to be specified are not limited to one location.

[0014] The rolling bearing cage of the present invention configured as described above has an arithmetic mean roughness (Ra) on the cage surface of 2 μm ≤ Ra ≤ 20 μm, so there are minute irregularities with an appropriate height difference, whereby as much lubricant as possible can be held on the cage surface.

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

[0016] In addition, as components that always or intermittently contact the surface of the cage, in addition to rolling elements, for example, inner members such as the inner ring of a rolling bearing or a shaft in a planetary gear mechanism, outer members such as the outer ring of a rolling bearing or a pinion gear in the planetary gear mechanism, or washers installed close to the width surface of the cage can be mentioned.

[0017] Therefore, even when the rolling bearing is used in a state where the supply of lubricating oil from the outside is blocked or insufficient, the cage can maintain the normal and stable rotation state of the rolling bearing for a required time without the temperature of the surface of the cage or the adjacent components rising, and a rolling bearing excellent in seizure resistance and wear resistance can be obtained by using such a cage.

[0018] In order to obtain such an action more stably, in the cage for a rolling bearing of the present invention, it is preferable that the root mean square roughness (Rq) of the roughness curve of the cage surface is 2 μm ≤ Rq ≤ 20 μm. If the Rq is within such a numerical range, the variation in the size of the irregularities on the cage surface is limited within the numerical range, so that the lubricant held on the cage surface can be efficiently, stably and continuously transferred to the components adjacent to the periphery of the cage.

[0019] Also, it is preferable that the average height (Rc) of the roughness curve of the cage surface is 10 μm ≤ Rc ≤ 70 μm. Since Rc, which is the average of the heights of the irregularities on the cage surface, is within such a numerical range, a sufficient amount of lubricant can be held on the cage surface, so that the supply amount of the lubricant from the cage surface to the components adjacent to the periphery of the cage is stable, and the normal and stable rotation state of the rolling bearing can be maintained more stably for a required time.

[0020] The cage for a rolling bearing having the above-described effects can be made of an appropriate synthetic resin or metal according to the purpose of use of the rolling bearing, and the surface of the cage can be prepared to have the above-described predetermined surface roughness by an existing molding method or surface treatment.

[0021] By rotatably supporting rolling elements using such a rolling bearing cage, for example, even in a dry-running state, a normal and stable rotation state of the rolling bearing can be maintained for a required time, thus creating a rolling bearing excellent in seizure resistance and wear resistance.

Advantages of the Invention

[0022] In this invention, by setting the arithmetic mean roughness (Ra) and the root mean square slope (RΔq) of the roughness curve of the surface of the cage of the rolling bearing within a predetermined numerical range of 2 μm ≤ Ra ≤ 20 μm and 10° ≤ RΔq ≤ 40°, the temperature of the lubricating oil on the surface of the cage for the rolling bearing and the parts close to the cage does not rise, and even in a state of insufficient lubricating oil, the friction coefficient of the cage surface is low and stable, enabling the normal and stable rotation state of the rolling bearing to be maintained for a required time. Furthermore, by using such a cage, there is an advantage that a rolling bearing excellent in seizure resistance and wear resistance can be created.

Brief Description of the Drawings

[0023]

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Best Mode for Carrying Out the Invention

[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 FIGS. 1 to 3, the synthetic resin cage 1A for a rolling bearing according to the first embodiment is an annular (substantially cylindrical) cage that rotatably holds the roller 4 (FIG. 1) of a rolling bearing (cage 1A and roller 4) that supports the pinion gear (planet gear) 3 incorporated in the planetary gear mechanism 2 (FIG. 3). The arithmetic mean roughness (Ra) of one or more cage surfaces selected from the inner surface (column part) 5a and the inner surface (end part) 5b of the rolling element pocket 5 that penetrates in the annular radial direction, the outer diameter surface 1a, the inner diameter surface 1b, and the 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°. It is a rolling bearing cage prepared as such.

[0026] As shown in FIG. 3, the planetary gear mechanism 2 includes a ring gear 6 having internal teeth and surrounding the outer periphery, a 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 the ring gear 6 and the sun gear 7, and the pinion shaft 8, which is a shaft engaging therewith, is supported by the pinion gear 3 and the roller 4 rotatably held by the cage 1A. Note that the end of the pinion shaft 8 is connected to the carrier 9 (Fig. 1), and the planetary gear mechanism 2 is driven by inputting and outputting the rotational force necessary for the revolution of the planetary gear from this carrier 9. In such a planetary gear mechanism 2, the inner diameter surface 3a of the pinion gear 3 corresponds to the inner peripheral surface of the outer ring of the rolling bearing, and the outer peripheral surface 8a of the pinion shaft 8 corresponds to the outer peripheral surface of the inner ring of the rolling bearing.

[0028] Also, an oil passage hole 10 for supplying lubricating oil (oil) is formed inside the pinion shaft 8. By guiding the lubricating oil 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 roller 4, the inner surfaces (columnar part) 5a and inner surfaces (end part) 5b of the rolling element retaining pocket 5, the outer diameter surface 1a, inner diameter surface 1b and the width surface 1c which is the axial end surface of the cage, lubrication of these rolling bearing parts is performed. Note that, of course, the surfaces of the outer claw and the inner claw that regulate the movement of the roller 4 in the radial outer or inner direction are included in the inner surface (columnar part) 5a of the rolling element retaining pocket 5.

[0029] Such a cage 1A made of synthetic resin has one or more predetermined surfaces selected from the inner surface (columnar part) 5a and inner surface (end part) 5b of the rolling element retaining pocket 5, the outer diameter surface 1a, inner diameter surface 1b and width surface 1c of the cage 1A within the predetermined numerical ranges of the above-mentioned surface roughness parameters Ra and RΔq, and further within the predetermined numerical ranges of Rq and Rc described later. It is prepared by using ordinary resin molding techniques such as injection molding and surface treatment techniques for its preparation.

[0030] That is, for example, by finishing the surface roughness of the mold used for injection molding or the like in advance within the numerical range of the above-mentioned predetermined roughness parameters by the following surface treatment, a rolling bearing cage having the above-mentioned predetermined surface properties can be manufactured.

[0031] Specifically, when machining a mold, profile (die profile) electrical discharge machining is performed to transfer the shape of the electrode to the workpiece. At this time, the roughness of the electrode used is finished to a desired roughness by surface treatment such as machining, shot blasting, or etching, and the surface of the mold is machined by electrical discharge using this electrode.

[0032] In addition to the roughness of the electrode, the necessary surface roughness can be adjusted by adjusting the swing of the electrode (the movement amount of the electrode) during electrical discharge machining, the gap between the machining surface and the electrode (gap, generally the discharge gap is 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 mold itself may be finished by blasting treatment such as sand blasting or shot blasting, etching treatment such as chemical etching or electrolytic etching, or machining. For example, in the case of chemical etching, the necessary surface roughness can be adjusted by adjusting the type, concentration, and chemical reaction time (etching time) of the etching solution.

[0033] As the type of synthetic resin for the cage material, it is preferable to adopt a thermoplastic resin from the viewpoints of preparing the surface properties and manufacturing efficiency. However, an appropriate resin can be adopted without particular restrictions according to the characteristics required for the rolling bearing.

[0034] For example, as a thermoplastic resin having excellent heat resistance and being melt-moldable, there is polyamide (PA) resin. By adopting PA10T (melting point 315 °C), PA9T (melting point 300 °C), etc., even when the bearing is exposed to a high-temperature environment, the cage can fully exhibit the expected performance.

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

[0036] Since PA10T is a resin material made from biomass-derived raw materials (for example, with a biomass content of approximately 37%), it also contributes to carbon neutrality and has few restrictions in terms of manufacturing costs. As a commercially available product of the above PA10T, for example, XecoT XG510A30D manufactured by Unitika Ltd. containing about 30% glass fiber can be used.

[0037] Also, the melting point of PA9T is lower than that of PA10T, but it is higher compared to other PA resins, and effects such as heat resistance equivalent to that of PA10T can be expected. As a commercially available product of the above PA9T, GENESTAR G1300A manufactured by Kuraray Co., Ltd. containing about 30% glass fiber can be adopted.

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

[0039] Such a metal cage is manufactured, for example, by using SPCC-SD or the like obtained by finishing a cold-rolled steel sheet to a dull finish (pearled surface), finishing the surface of the rolling roll during cold rolling to have the required roughness according to this invention, performing cold rolling with this roll to obtain a coil material, and then press-working this coil material.

[0040] Alternatively, after manufacturing a cage by press-working a commercially available cold-rolled steel sheet such as SPCC-SD, blast treatment, etching treatment, or machining may be performed on the outer diameter surface, inner diameter surface, guide surface, and width surface of the pocket portion of the cage to finish it to a surface having the required roughness according to this invention.

[0041] That is, even in the case of a metal annular cage instead of a synthetic resin cage, the inner surface (column part) 11a, the inner surface (end part) 11b of the pocket 11 that radially penetrates the cage 1B, the outer diameter surface 1d and the inner diameter surface 1e of the cage 1B, or one or more cage guide surfaces or width surfaces 1f selected from these are cold-rolled with a rolling roll having the above-mentioned required roughness, or the surface roughness of the cage guide surface or width surface can be adjusted to the required roughness by subjecting the cage manufactured by press working to blasting treatment, etching treatment, or machining.

[0042] The inner surface 5b (FIG. 2) or 11b (FIG. 4) in the first and second embodiments is a part that may come into contact with the end surface of the roller 4, and the width surface 1c or width surface 1f is a part that may come into contact with the washer 12, which is a fixing part in the width direction. That is, as a possible usage situation of such a rolling bearing, when a situation (referred to as skew) occurs in which the rotation axis of the roller is not parallel to the central axis, a phenomenon called lateral run occurs in which the roller and the cage move in the axial direction. At this time, an axial load (induced axial load) is generated in the bearing, and damage such as wear may occur on the inner surface 5b or inner surface 11b that the roller is likely to contact, and the width surface 1c or width surface 1f that is likely to contact fixing parts such as the washer 12. For these reasons, it is effective to set the surface roughness of the inner surface 5b or inner surface 11b and the width surface 1c or width surface 1f within the predetermined numerical range described in the present invention.

[0043] Thus, the roughness parameters required for the predetermined surface of the cage common to the first and second embodiments described above are such that the arithmetic mean roughness (Ra) 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°.

[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 average height (Rc) of the roughness curve is 10 μm ≤ Rc ≤ 70 μm.

[0045] Ra, which is a parameter of surface roughness, is the average value of the height difference from the average plane of the contour shape. It is a parameter that is less affected by disturbances such as scratches, dust, and noise and can obtain stable results.

[0046] Rq is a roughness parameter obtained by taking the square root after calculating the average value by squaring the variation in unevenness with respect to the reference plane, and is sometimes called the RMS value. Since Rq emphasizes high protrusions by squaring the variation in unevenness and the value increases when there are large unevennesses, it is suitable for evaluating both average variation and large unevenness.

[0047] When Ra and Rq are less than 2 μm, it becomes difficult for lubricating oil to flow in and out of the gap between the cage surface and the raceway surface or rolling surface, or between the cage surface (width surface) and the fixing parts in the width direction. When conditions outside the predetermined numerical range of RΔq described later are added, it becomes difficult to improve seizure resistance and reduce the friction coefficient and temperature rise.

[0048] When Ra and Rq are greater than 20 μm, the variation in the dimensions of the completed cage unit becomes large, it becomes difficult to ensure dimensions, and it becomes difficult to ensure shape accuracy (roundness, cylindricity, etc.). It becomes difficult to set the guide gap (the gap between the cage and the raceway ring or rolling elements) to the desired gap. In addition, the contact state with the bearing raceway surface becomes non-uniform. When conditions outside the predetermined numerical range of RΔq described later are added, the friction coefficient, the rise in bearing temperature, and even the life of the rolling bearing may become shorter than expected.

[0049] RΔq (also called Δq and Rdq) represents the root mean square of the square of the local slope of the roughness curve and is a parameter for evaluating the magnitude of the local inclination angle. It quantifies the steepness of the surface unevenness. The larger the value of RΔq, the larger the inclination angle of the local (peak) of the cross-sectional curve.

[0050] By setting 10° ≤ RΔq ≤ 40°, the roughness shape (local inclination angle) of the cage surface that contacts the mating surface (bearing raceway surface, rolling surface, width-direction fixed part width surface) can be optimized, and the lubricant held on the cage surface can be efficiently and continuously transferred to one or more of the inner ring (inner member), outer ring (outer member), rolling elements, or width-direction fixed parts on the mating side.

[0051] When RΔq is less than 10°, it becomes difficult for lubricating oil to flow in and out between the cage surface and the mating surface, making it difficult to improve seizure resistance, reduce the friction coefficient, and reduce the temperature rise of the bearing. When RΔq is greater than 40°, the contact area between the tip of the convex part of the cage surface and the mating part becomes small, and wear and deformation of the tip of the convex part tend to progress due to contact with the mating surface, which is not preferable. For these reasons, a more preferable RΔq is 10° ≤ RΔq ≤ 30°, and more preferably 15° ≤ RΔq ≤ 25°.

[0052] Also, Rc is a parameter representing the average value of the height of the profile curve elements at the reference length. The profile curve elements refer to a set of adjacent peaks and valleys, and the average value of the height difference between the peak and the valley is the average height of the roughness curve elements.

[0053] By setting the average height Rc of the roughness curve of the cage surface to 10 μm ≤ Rc ≤ 70 μm, the roughness (concavities and convexities of the contour shape) of the cage surface can be managed, and a sufficient amount of lubricant can be stably held on the cage surface. When Rc is less than 10 μm, it becomes difficult for lubricating oil to flow in and out between the cage surface and the raceway surface or rolling surface, or between the cage surface (width surface) and the width-direction fixed parts. When conditions outside the predetermined numerical range of RΔq described later are added, it becomes difficult to improve seizure resistance and reduce the friction coefficient.

[0054] Also, when Rc is larger than 70 μm, the dimensional variation of the finished cage alone becomes large, making it difficult to secure dimensions and difficult to ensure shape accuracy (roundness, cylindricity, etc.). It becomes difficult to set the guiding clearance (the clearance between the cage and the raceway ring or rolling elements) to the desired clearance. In addition, when the contact state with the bearing raceway surface becomes non-uniform and conditions outside the predetermined numerical value range of RΔq described later are added, it leads to an increase in the friction coefficient and temperature, as well as a short bearing life.

[0055] The types of rolling bearings of the first embodiment and the second embodiment described above are exemplified by needle bearings (needle roller bearings), but are not limited thereto, and may be cylindrical roller bearings, tapered roller bearings, self-aligning roller bearings, ball bearings, etc.

Example

[0056] [Example 1] As a molding material for the resin cage, a polyamide resin (PA10T) containing 30% glass fiber (manufactured by Unitika Ltd.: XecoT XG510A30D) was used, and injection molding was performed using a mold for texture (a mold with a surface roughness of about RΔq 19°, Ra 7 μm, Rq 9 μm, and Rc 27 μm) to form a resin cage in the form shown in Fig. 2, in which the inner surface of the pocket for holding rolling elements, the outer diameter surface, and the inner diameter surface of the cage are formed with texture surfaces having the above-mentioned roughness.

[0057] Also, using a mold for forming test pieces, which has a texture surface with the same surface roughness as the above-mentioned mold for texture, three plate-shaped test pieces (40 mm × 40 mm) 13 shown in Fig. 5 were produced.

[0058] For each test piece, the surface roughness parameters RΔq, Ra, Rq, and Rc were measured with a surface roughness measuring instrument. RΔq, Ra, Rq, and Rc are parameters of the standards shown in JIS B0601:2013. The measurement conditions were to measure any two locations on the surface of each test piece in the XY direction with a measurement length of 15 mm, an evaluation length of 12.5 mm, a cut-off λ C 2.5 mm, λ s 0.008 mm, calculate their average values, and show these as measurement results in Table 1, Fig. 6, or Fig. 7.

[0059]

Table 1

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

[0061] [Comparative Example 2] As a molding material for the metal holder, SPCC of cold-rolled steel sheet was used, cold-rolled to form a coil material using a roll with a dull finish commonly used for the surface of the rolling roll during cold rolling, and this coil material was press-worked to mold a rolling bearing holder shown in FIG. 4 and to produce three plate-shaped test pieces (40 mm × 40 mm) 13 shown in FIG. 5. For each test piece, in the same manner as in Example 1, the surface roughness parameters RΔq, Ra, Rq, and Rc were measured, and the results are shown in Table 1, FIG. 6, or FIG. 7.

[0062] Next, the following Friction and Wear Tests 1 and 2 were conducted on the test pieces of Example 1 and Comparative Examples 1 and 2 obtained as described above.

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

[0064] Note that the above oil 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 Fig. 8 or Fig. 9.

[0065] <Friction and Wear Test 2 (State of Natural Oil Removal)> In Friction and Wear Test 1, except for using the test pieces 13 of Example 1 and Comparative Examples 1 and 2 in the state of natural oil removal, the changes over time in the friction coefficient and the temperature of the cylindrical jig were measured in exactly the same way, and the results are shown in Fig. 10, Fig. 11 or Fig. 12. Note that the above "state of natural oil removal" refers to a state in which a plate-shaped test piece is immersed in oil at room temperature, then taken out of the oil, and left for 24 hours with the plate surface almost vertical, and Friction and Wear Test 2 was carried out without lubrication as it was.

[0066] Also, the above metal cylindrical jig 14 was made of S45C material, and for both Friction and Wear Test 1 and Friction and Wear Test 2, those with the contact surface with the test piece polished with #2000 before the test of each test piece were used.

[0067] From the results of the surface roughness measurement and Friction and Wear Tests 1 and 2 for the above Example 1 and Comparative Examples 1 and 2, the following evaluations are made.

[0068] As shown in FIGS. 6 to 12, in Example 1 where the surface roughness parameters of the test piece were Ra 2 μm or more and RΔq 10° or more, in both the oil immersion state (FIG. 8) and the natural oil removal state (FIG. 10), the change in the coefficient of friction over time in the friction and wear test was small. The oil temperature during the test was about 33° C. or lower and was low and stable (FIG. 9). The temperature of the cylindrical jig in the natural oil removal state of Example 1 (FIG. 12) was stable at about 60 to 70° C. for about 10 to 15 minutes after the start of the test. However, after 10 to 15 minutes when it was considered that the oil held on the surface of the test piece was removed by scattering, the temperature rose rapidly and reached about 200° C. However, the temperature of the cylindrical jig in Example 1 was lower than that in Comparative Examples 1 and 2 and did not melt.

[0069] On the other hand, for the test pieces of Comparative Examples 1 and 2 where the surface roughness parameters of the test piece were less than Ra 2 μm and less than RΔq 10°, the coefficient of friction became unstable and increased significantly within about 1 to 2 minutes even in the oil immersion state (FIG. 8). Also, the oil temperature 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, for the test piece of Comparative Example 1, the coefficient of friction fluctuated greatly within about 2 to 3 minutes in the natural oil removal state, became unstable, and the resin test piece melted around 10 minutes.

[0071] Also, for the test piece of Comparative Example 2, the coefficient of friction became unstable within 2 to 4 minutes, a large metallic sound was generated, the thermocouple came off from the cylindrical jig and temperature measurement became impossible, and the temperature of the cylindrical jig of the test piece where the thermocouple did not come off became a high temperature exceeding 200° C. within a few minutes.

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

Industrial Applicability

[0073] For example, like rolling bearings incorporated in a reduction mechanism or a transmission mechanism such as an e-Axle of an automobile, an automatic transmission (AT), or a continuously variable transmission (CVT), rolling bearings lubricated with an insufficient amount of lubricant or a low-viscosity lubricant, high-speed rotating rolling bearings, a cage for rolling bearings for which it is required to minimize the rotational torque and heat generation of the bearings as much as possible, or a rolling bearing provided with such a cage, can be widely used industrially.

Explanation of Reference Numerals

[0074] Cages 1A and 1B Outer diameter surfaces 1a and 1d Inner diameter surfaces 1b and 1e Width surfaces 1c and 1f Planetary gear mechanism 2 Pinion gear 3 Inner diameter surface 3a of the pinion gear Roller 4 Pockets 5 and 11 Inner surfaces (column parts) 5a and 11a Inner surfaces (end parts) 5b and 11b Ring gear 6 Sun gear 7 Pinion shaft 8 Outer peripheral surface 8a Carrier 9 Oil passage hole 10 Washer 12 Test piece 13 Cylindrical jig 14

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 being 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 mean 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 Claim 4.

7. A needle bearing provided with the cage according to Claim 4.

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

9. A rolling bearing provided with the cage according to Claim 5.

10. A needle bearing provided with the cage according to Claim 5.

11. A planetary gear mechanism in which a planetary gear is supported by the needle bearing according to Claim 10.

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