JP2015200355A - rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing capable of extending a seizure life of the bearing, keeping lubricant oil film for a long period of time, and restricting occurrence of rapid increasing in temperature or seizure by applying a high degree of surface roughness to at least a sliding contact surface of a cage so that base oil is expanded over the surface of the cage from the adhered grease due to capillary phenomenon to supply lubricant to the sliding contact surface.SOLUTION: This invention relates to a bearing comprising an inner ring, an outer ring, a plurality of rolls, a plurality of pockets for rotatably holding the plurality of rolls, and a guided surface guided by the inner ring or the outer ring and a cage. A surface roughness of the guided surface and a surface roughness of an inner surface of the pocket show an arithmetic average roughness Ra of 0.5 to 10 μm.

Description

  The present invention relates to a rolling bearing.

  Generally, rolling bearings such as cylindrical roller bearings and angular ball bearings are used as bearings for main spindles of machine tools. As the cage for these rolling bearings, a so-called plastic cage (synthetic resin cage) made of a cotton cloth-reinforced phenolic resin or a polyamide 66 resin reinforced with glass fiber is used. It is done. Since the plastic cage is lightweight, it has a small centrifugal force during rotation and is self-lubricating, which is advantageous for high-speed rotation. In rolling bearings for high-speed rotation using these plastic cages, an outer ring guide system in which the cage is rotated and guided by a bearing outer ring is usually employed.

  In addition, as a lubrication method for these rolling bearings, grease lubrication, oil-air lubrication, jet lubrication, etc. are appropriately selected depending on the use conditions and cost, but generally they are low in cost and easy to maintain. Grease-filled lubrication by initial filling is often used.

  Incidentally, in recent years, in the field of machine tools, there is a tendency to improve the cutting ability and shorten the machining time, and accordingly, the tendency to increase the rotation speed of the main spindle is remarkable. For this reason, the amount of lubricating oil supplied to the bearing that supports the main shaft that rotates at high speed also tends to be very small (the minimum amount necessary).

  However, when the lubricating oil is not supplied from the outside to the inside of the bearing during rotation, such as grease lubrication, the lubricating oil film tends to be interrupted due to a temporary or continuous shortage of lubricating oil over time. End up. Under such severe lubrication conditions, it is difficult to obtain sufficient lubrication.

  Patent Document 1 describes that a small miniature ball bearing retainer corresponding to HDD, LBP or the like has a retaining portion for retaining a rolling element, and the inner surface of the retaining portion is roughened. By doing so, it is intended to improve the holding power of the base oil in the holding portion.

Japanese Patent Laid-Open No. 11-108064

  However, in the miniature ball bearing described in Patent Document 1, only the inner surface of the holding portion of the cage is roughened, and it is not assumed to be used in a high speed range like the outer ring guide type rolling bearing described above. it is conceivable that. In bearings in which the cage is guided to the outer ring or inner ring, not only the sliding part between the cage and rolling element, but also the sliding part between the cage and outer ring or inner ring generates heat and becomes hot. There was a case where the problem of being burned down and stopping the rotation occurred. Even if grease is filled, only a small part is actually used for lubrication, and the retainer inner peripheral surface of the seized bearing (in the case of outer ring guide), seal back surface, outer ring inner peripheral surface (pocket guide) In the case of inner ring guides, etc.), there is a fact that grease containing sufficient base oil adheres without being used, and by effectively using these greases, the seizure life is further extended. There was room.

  The present invention has been made in view of the above-described problems, and the purpose thereof is at least on the sliding surface of the cage (the pocket inner surface, the outer peripheral surface in the case of the outer ring guide, the inner peripheral surface in the case of the inner ring guide). By providing a large surface roughness, the base oil spreads from the grease attached to the surface of the cage due to capillarity, supplying lubricant to the sliding contact surface such as the pocket inner peripheral surface, and the seizure life of the bearing Rolling that can maintain a lubricating oil film over a long period of time and suppress the occurrence of rapid temperature rise and seizure, even when used for high-speed rotating parts such as machine tool spindles It is to provide a bearing.

The above object of the present invention can be achieved by the following constitution.
(1) An inner ring having an outer peripheral surface on which an inner ring raceway surface is formed, an outer ring having an inner peripheral surface on which an outer ring raceway surface is formed, and an inner ring raceway surface and an outer ring raceway surface that are movably disposed. A rolling bearing comprising: a plurality of rolling elements, a plurality of pockets that hold the plurality of rolling elements in a freely rolling manner, and a cage that is guided by the inner ring or the outer ring. The rolling bearing is characterized in that the surface roughness of the guided surface and the surface roughness of the inner surface of the pocket have an arithmetic average roughness Ra of 0.5 to 10 μm.
(2) The rolling according to (1), wherein the arithmetic average roughness Ra of at least one of the peripheral surfaces or end surfaces which are not guided surfaces of the cage is 0.5 to 10 μm. bearing.

  According to the present invention, by imparting a large surface roughness to at least the sliding surface of the cage (inner surface of pocket, outer peripheral surface in the case of outer ring guide, inner peripheral surface in the case of inner ring guide), by capillary action, Base oil spreads from the grease adhering to the surface of the cage, supplies lubricant to the sliding contact surface such as the inner surface of the pocket, further extends the seizure life of the bearing, and rotates at high speed such as the spindle of a machine tool. Even if it is a case where it is used for a member, a lubricating oil film can be maintained over a long period of time, and rapid temperature rise and the occurrence of image sticking can be suppressed.

It is principal part sectional drawing of the angular ball bearing which concerns on embodiment of this invention. It is sectional drawing which shows the spindle apparatus as a bearing testing machine. Relation between arithmetic mean roughness and specific travel distance Explanation of base oil travel distance

Hereinafter, an embodiment of a rolling bearing according to the present invention will be described in detail with reference to the drawings.

  An angular ball bearing 1 as a rolling bearing according to the present embodiment is used for a member that rotates at high speed, such as a spindle of a machine tool, and an outer ring 2 having an outer ring raceway surface 2a on an inner peripheral surface and an inner ring raceway surface 3a on an outer peripheral surface. A plurality of balls 4 that are arranged to freely roll with a contact angle α between the inner ring 3 and the outer ring raceway surface 2a and the inner ring raceway surface 3a, and hold the plurality of balls 4 at predetermined intervals in the circumferential direction. And a pair of oil seals that are respectively disposed so as to close both axial openings of the bearing space existing between the inner peripheral surface of the outer ring 2 and the outer peripheral surface of the inner ring 3 and seal the bearing interior. 5 is provided. The angular ball bearing 1 is used in grease-filled lubrication that is lubricated by grease initially sealed in the bearing space.

  The cage 10 is formed at a predetermined interval in the circumferential direction, and has a plurality of cylindrical pockets 11 for holding the balls 4. The pocket 11 has an inner surface 11 a on which the balls 4 abut. Further, in the cage 10, the guided surface 12 a (outer peripheral surface) of one (right side in FIG. 1) of the pair of ring portions 12 positioned on both sides in the axial direction is the outer ring raceway surface of the outer ring 2. This is an outer ring guide system that is guided by the guide surface 2b (inner peripheral surface) on the counter-bore side with respect to 2a. The cage 10 also has a peripheral surface 12 b (inner peripheral surface) and an end surface 13 that are not guided surfaces of the ring portion 12.

  Here, the cage 10 is formed by injection molding using engineering plastics such as PPS (polyphenylene sulfide) as a main material, and the guided surface 12a and the inner surface 11a of the ring portion 12 from the mold at the time of the injection molding, preferably The surface roughness larger than usual is transferred to the peripheral surface 12b (inner peripheral surface) and the end surface 13 which are not guided surfaces. Here, the structure provided by the mold at the time of injection molding is that a skin layer is formed on the surface of the guided surface 12a and the inner surface 11a due to the high temperature of the material at the time of injection molding, thereby improving the wear resistance. It is because it improves.

  Specifically, the surface roughness given to the guided surface 12a and the inner surface 11a of the cage 10 is set such that the arithmetic average roughness Ra is 0.5 to 10 μm. As a result, the grease is held in the concave portion forming the surface roughness, and the grease is applied to the contact interface between the guided surface 12a of the cage 10 and the guide surface 2b of the outer ring 2 and the contact interface between the inner surface 11a and the ball 4 from the concave portion. Therefore, the oil film can be formed at the contact interface without interruption. Moreover, it is preferable that arithmetic mean roughness Ra of at least one of the peripheral surfaces or end surfaces which are not guided surfaces of the cage is 0.5 to 10 μm. According to the present invention, at least the sliding surface of the cage (the inner surface of the pocket, the outer peripheral surface in the case of the outer ring guide, the inner peripheral surface in the case of the inner ring guide) or the peripheral surface 12b (in the case of the outer ring guide) that is not the guided surface. By giving a large surface roughness to the inner peripheral surface and inner ring guide (the outer peripheral surface) and the end surface 13 etc., the base oil spreads from the grease adhering to the cage surface due to capillary action, and the inner surface of the pocket Even if the lubricant is supplied to the sliding contact surface such as 11a to further extend the seizure life of the bearing and used for a high-speed rotating member such as a spindle of a machine tool, the lubricating oil film is maintained over a long period of time. In addition, it is possible to suppress the rapid temperature rise and the occurrence of image sticking.

  The cage 10 may be reinforced with a filler such as glass fiber or carbon fiber in order to improve wear resistance and mechanical strength. However, the guided surface 12a and the outer ring 2 of the cage 10 may be provided. There is a possibility that the wear powder including the filler generated at the contact interface with the guide surface 2b and the contact interface between the inner surface 11a and the ball 4 acts as a foreign substance, and the cutting wear increases. However, in the present embodiment, the wear powder is easily removed from the contact interface by the unevenness formed in the cage 10, and the wear resistance can be improved.

  Thus, even when the lubrication conditions become severe due to high-speed rotation, the oil film is formed without interruption at the contact interface, and wear powder is easily discharged from the contact interface. Can be suppressed over a longer period of time than before.

  In addition, in the range where the arithmetic average roughness Ra is less than 0.5 μm, the amount of grease retained in the concave portion forming the surface roughness decreases, and the contact interface between the guided surface 12a of the cage 10 and the guiding surface 2b of the outer ring 2 Insufficient grease will be supplied. Further, when the arithmetic average roughness Ra exceeds 10 μm, the roughness itself may adversely affect the rotation accuracy of the spindle bearing for machine tools that require high-precision and high-speed rotation.

(Example)
Next, an outer ring guide type angular contact ball bearing 1 (model number: 70BNR10HTV1V) as shown in FIG. 1 was incorporated into a spindle device 20 as a bearing tester as shown in FIG. 2 to evaluate the seizure life.

  The spindle device 20 is a spindle device for a machine tool, and a rotary shaft 21 has two rows of angular ball bearings 1 and 1 (front bearings) that support the tool side (axially forward, left side in FIG. 2); The housing H is rotatably supported by two rows of rear bearings 60 and 60 that support the side opposite to the tool (back in the axial direction, right side in FIG. 2). The housing H includes a front lid 31, an outer cylinder 33, and a rear lid 34 in order from the tool side. A tool mounting hole 24 formed in the axial direction through the axis center is provided on the tool side of the rotating shaft 21, and the tool mounting hole 24 is used for mounting a tool (not shown) such as a cutting tool to the rotating shaft 21. used.

  Then, the endurance test of the angular ball bearing 1 was performed by rotationally driving the rotating shaft 21 at a rotational speed of 16000 min-1 (dmn value: 1.42 million) by a motor (not shown). The amount of grease sealed in each angular ball bearing 1 was set to 2.6 g, and the outer cylinder 33 constituting the housing H was cooled by a cooling mechanism (not shown) during the durability test.

  Here, as shown in Table 1, the surface roughness of the end surface 13 is different from that of the angular ball bearing 1 on the outer peripheral surface that is the guided surface 12a, the pocket inner surface 11a, and the inner peripheral surface of the peripheral surface 12b that is not the guided surface. The cage 10 made of PPS-CF30, which is a PPS material formed by injection molding, was applied, an endurance test was performed, and the specific seizure life was measured. The surface roughness of the guided surface 12a was given by an injection mold. Further, the cage 10 of Comparative Example 2 does not perform any treatment on the guided surface 12a or the like.

  Table 1 shows the result of measuring the seizure life by measuring the temperature of the outer ring 2, and the seizure life of Comparative Example 2 is represented as 1. In Examples 1 to 3 in which the arithmetic average roughness Ra of the guided surface 12a and the pocket inner surface is set in a range of 0.5 to 10 μm, the seizure life is improved as compared with Comparative Examples 1 and 2, and the processing is rough. It can be seen that the lifespan is further improved by increasing the number of sites to perform. This is because, even after the endurance test, the recessed portion constituting the surface roughness remains on the guided surface 12a, the grease is easily held, and the guided surface 12a of the cage 10 and the guiding surface 2b of the outer ring 2 Due to lubrication, the effect of assisting lubrication between the pocket inner surface 11a and the ball 4, and the capillary phenomenon, the base oil spreads from the grease attached to the cage surface, the guided surface 12a of the cage 10 and the inner surface 11a of the pocket. This is considered to be due to the effect of supplying the lubricant to the sliding contact surface.

  Moreover, the test piece which changed the arithmetic mean roughness of the surface in the flat plate using PPS-CF30 as a resin material was created, the grease was apply | coated to the surface, and the extent of oil spread on the surface was measured. The results are shown in FIG. 3 as the relationship between the arithmetic average roughness and the specific movement distance. The “specific movement distance” in FIG. 3 is the ratio of the distance in which the base oil in the grease spreads from the interface between the initially applied grease and the flat plate, as shown in FIG. 4, and Ra = 2.0 μm distance Is the ratio when. As shown in FIG. 3, when the arithmetic average roughness Ra is 0.5 μm to 10 μm, preferably 1 μm to 10 μm, more preferably 2 μm to 10 μm, the base oil in the grease spreads on the flat plate due to capillary action. I can see it going. From this result, by setting the arithmetic average roughness Ra within the above range, the base oil spreads from the grease adhering to the cage 10, and the guided surface 12 a of the cage 10, the inner surface 11 a of the pocket, etc. It is considered that there is an effect of supplying a lubricant to the sliding contact surface.

  In addition, this invention is not limited to each embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.

  For example, in the above-described embodiment, the outer ring guide method in which the cage 10 is guided to the outer ring 2 is described, but an inner ring guide method may be used. In this case, the surface roughness of the guided surface (inner peripheral surface) of the cage guided by the guide surface (outer peripheral surface) of the inner ring and the inner surface of the pocket is set to at least an arithmetic average roughness Ra of 0.5 to 10 μm. Preferably, the arithmetic average roughness Ra of at least one of the outer peripheral surface or end surface which is not the guided surface of the cage is set to 0.5 to 10 μm. With this configuration, the oil film is formed without interruption at the contact interface between the guided surface of the cage and the guide surface of the inner ring, and wear powder is easily discharged from the contact interface. Can be suppressed for a longer period of time than before, and the base oil spreads from the grease adhering to the cage 10 to expand the surface of the cage, and the sliding contact between the guided surface 12a of the cage 10 and the inner surface 11a of the pocket, etc. It is considered that there is an effect of supplying a lubricant to the surface.

  Further, in the above-described embodiment, the surface roughness is given to the inner surface 11a with which the balls 4 abut out of the pockets 11 of the cage 10, but the surface roughness is given to the entire surface of the pocket 11 of the cage 10. It doesn't matter.

  Further, the rolling bearing is not limited to the angular ball bearing, and may be any rolling bearing such as a cylindrical roller bearing.

1 Angular contact ball bearings (rolling bearings)
2 Outer ring 2a Outer ring raceway surface 2b Guide surface 3 Inner ring 3a Inner ring raceway surface 4 Ball (rolling element)
5 Oil seal 10 Cage 11 Pocket 11a Inner surface 12 Ring portion 12a Guided surface 12b Peripheral surface 13 not guided surface 13 End surface 20 Spindle device 21 Rotating shaft 24 Tool mounting hole 31 Front cover 33 Outer cylinder 34 Rear cover 60 Rear bearing H Housing α Contact angle

Claims (2)

  An inner ring having an outer peripheral surface on which an inner ring raceway surface is formed, an outer ring having an inner peripheral surface on which an outer ring raceway surface is formed, and a plurality of rollers disposed between the inner ring raceway surface and the outer ring raceway surface so as to be capable of rolling. A rolling bearing comprising: a rolling element, a plurality of pockets for freely rolling the plurality of rolling elements, and a cage having a guided surface guided by the inner ring or the outer ring. A rolling bearing characterized in that the surface roughness of the guided surface and the surface roughness of the inner surface of the pocket have an arithmetic average roughness Ra of 0.5 to 10 μm. 2. The rolling bearing according to claim 1, wherein an arithmetic average roughness Ra of at least one of a peripheral surface or an end surface which is not a guided surface of the cage is 0.5 to 10 μm.

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