JP2006300183A - Ultrathin-walled roller bearing and cage for ultrathin-walled roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrathin-walled roller bearing and a cage for the ultrathin-walled roller bearing capable of surely preventing the coming-off of the cage. <P>SOLUTION: The cage 21 for the ultrathin-walled roller bearing is constituted of a plurality of arc segments 22, the segments 22 are connected annularly in an endless form without having no-connection part along the circumferential direction. The segments are connected annularly, and the cage has an endless form without having no-connection part along the circumferential direction. Therefore, the coming-off of the cage can be surely prevented even if a bearing attachment failure occurs such as in the bad attachment environment of the bearing, that is, in the usage environment to deform the bearing, or the case that the inside design of the bearing is special design such as a four-point contact ball bearing having different right and left contact angles. Therefore, the reliable ultrathin-walled roller bearing can be achieved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultra-thin type rolling bearing used in, for example, industrial robots, machine tools, medical equipment, and the like, and a cage incorporated in the bearing.

  FIG. 5 shows an example of a CT scanner device which is a kind of medical equipment. As shown in the figure, in the CT scanner apparatus, X-rays generated by the X-ray tube apparatus 1 are subjected to a subject through a wedge filter 2 for making the intensity distribution uniform and a slit 3 for limiting the intensity distribution. 4 is irradiated. X-rays that have passed through the subject 4 are received by the detector 5, converted into electrical signals, and sent to a computer (not shown).

  Each component such as the X-ray tube device 1, the wedge filter 2, the slit 3, and the detector 5 in this CT scanner device is provided on a substantially cylindrical rotating gantry 8 that is rotatably supported by a fixed gantry 7 via a bearing 6. It is mounted and rotated around the subject 4 by the rotational drive of the rotary mount 8.

  In the CT scanner device, projection data covering all angles in the examination section of the subject 4 is obtained by the rotational movement around the subject 4 of the X-ray tube device 1 and the detector 5 opposed to each other, and from these data, A tomographic image is obtained by a preprogrammed reconstruction program.

  In this CT scanner device, the inner peripheral surface of the fixed gantry 7 is formed to have a large diameter (approximately 1 m in diameter) that allows the subject 4 to enter. A bearing having a remarkably small cross section with respect to the diameter, that is, a so-called ultrathin rolling bearing is used.

  Conventionally, resin-made split cages are frequently used for ultra-thin type rolling bearings for CT scanner devices. As shown in FIG. 6, this type of cage 11 has an end-like structure in which a plurality of arc-shaped segments 12 are coupled in the circumferential direction and a non-connecting portion 13 is provided in a part thereof. As shown in FIG. 7, the segment 12 includes an arc-shaped base portion 14, a column portion 15 extending in a cantilever manner from the base portion 14, and a plurality of pockets 16 a and 16 b formed between adjacent column portions 15. It has. The column portion 15 extends in the axial direction beyond the pitch circle of the rolling elements 18 indicated by a one-dot chain line in FIG. The pockets 16a and 16b in the illustrated example have two types of shapes. That is, the first pocket 16a having a wall surface closer to the rolling element insertion portion (upper side in the figure) than the center of the pocket (in the above-mentioned pitch circle in the figure) as a concave arc surface in plan view, The second pocket 16b is a straight surface. The first pockets 16a and the second pockets 16b are alternately arranged in the circumferential direction. In both cases, the cross section in the radial direction (the cross section perpendicular to the drawing sheet) is a concave curved surface with the center of curvature as the center of curvature.

  The rolling elements 18 are incorporated into the pockets 16a and 16b by pushing the rolling elements 18 from the rolling element insertion portions of the pockets 16a and 16b to the back side. At this time, in the first pocket 16a, it is necessary to push the rolling element 18 while expanding the column part 15 on the entrance side, but in the second pocket 16b, such trouble is not required, so the rolling element to the cage 11 is required. Eighteen assembling steps can be simplified. Note that the shape and structure of the pockets described above are merely examples, and pockets having various shapes and structures can be used depending on the use conditions of the bearing, such as a single pocket.

At both ends of each segment 12, connecting portions 17a and 17b for connecting adjacent segments are provided. Here, the connection part 17b which carries out uneven engagement with the connection part 17a of the segment 12 used as a connection partner in the circumferential direction is illustrated. One connecting portion 17a has a convex shape with a wide front end side. In the example shown in the figure, the connecting portion 17a is composed of a substantially cylindrical surface portion extending in the radial direction of the cage 11 and a neck portion narrower than that. Yes. The other connecting portion 17b is formed in a cylindrical concave shape that matches the convex connecting portion described above. When connecting adjacent segments, the connecting portion 17 a of one segment 12 is pushed in the radial direction with respect to the connecting portion 17 b of the other segment 12. Thereby, connection part 17a, 17b fits and the isolation | separation of the circumference direction of segments is prevented (for example, refer patent document 1, 2).
JP 2004-19921 A JP 2004-162879 A

  By the way, in the bearing equipped with the cage 11 composed of a plurality of segments 12, when assembling the bearing, the segments 12 are connected as described above, and the rolling elements 18 are incorporated into each pocket. In consideration of the assemblability, as shown in FIG. 6, a non-connecting portion 13 is provided at one place in the circumferential direction of the cage 11, and the segment 12 is connected from the end portion 11 a located at the non-connecting portion 13. By assembling between the inner and outer rings, the cage 11 can be easily assembled.

  The above-described segment 12 constituting the cage 11 is a resin injection-molded product, and a fiber reinforced polyamide resin (PA66) is generally adopted as the material thereof. However, since this PA66 has a linear expansion coefficient larger than that of steel, which is a bearing ring material for bearings, the dimensional difference increases due to temperature change, and the PA66 has a property of expanding due to water absorption, so that it is used in a CT scanner device. In the case of large bearings, the cage circumferential length changes significantly. In order to absorb this change in the circumferential length of the cage, the unconnected portion 13 is provided at one circumferential direction of the connected segments 12.

  However, providing the non-connecting portion 13 to the cage 11 to improve the assembly also means that the cage 11 can be easily removed. From this, when there is a defect in the bearing mounting portion and the bearing race is deformed, this deformation increases the advance delay of the rolling element 18 in the circumferential direction of the cage 11 when the bearing rotates, and the cage 11 There is a possibility of dropping off from the end portion 11a. Further, not only the above-described disturbance from the periphery of the bearing, but also in the case of the design of the bearing (for example, a special design in which the contact angle on the left and right is different for a four-point contact ball bearing), There is a possibility that the retainer 11 falls off. It is demanded to determine under what conditions the dropping of the cage 11 may occur and to take countermeasures.

  Therefore, the applicant of the present invention proposes the present invention as a result of examining and considering the mechanism of the cage dropout, and the purpose thereof is an ultra-thin wall that can reliably prevent the cage dropout. An object of the present invention is to provide a cage for a rolling bearing and an ultra-thin rolling bearing.

  As a technical means for achieving the above object, the present invention provides an ultra-thin type rolling bearing retainer composed of a plurality of arc-shaped segments, wherein the segments are connected in an annular shape and the circumferential direction thereof. It is characterized by having an endless shape having no unconnected portion. The segments constituting the cage are preferably made of a resin such as PPS (polyphenylene sulfide). In addition, the cage having the above-described configuration can be combined with a plurality of rolling elements incorporated between the races of the inner ring, the outer ring, and the inner and outer rings to form an ultra-thin type rolling bearing. The cage in the ultra-thin type rolling bearing exhibits a function of holding a plurality of rolling elements at a predetermined interval in the circumferential direction.

  In the ultra-thin type rolling bearing having the above-described configuration, either the outer ring or the inner ring is fixed to the rotating base of the CT scanner device that rotates around the subject, and the other is fixed to the fixed base of the CT scanner device. With such a configuration, a highly reliable CT scanner device can be provided.

  Here, the applicant of the present invention incorporated an ultra-thin type rolling bearing incorporating a conventional cage having an end portion having a non-connecting portion and an endless retainer of the present invention having no end portion. On the other hand, a test was conducted assuming that the ultra-thin type rolling bearing was mounted on a CT scanner device. As a result of the test, the conventional cage was dropped from the inner and outer rings, and the cage of the present invention was not dropped from the inner and outer rings. As a result, in the cage of the present invention, disturbances from the periphery of the bearing (for example, a mounting failure of the bearing) and bearing design (for example, a special design in which the left and right contact angles are different in a four-point contact ball bearing) It is possible to surely prevent the dropout.

  The present applicant considered the dropping mechanism of the conventional cage 11, that is, the end-cage cage 11 having the non-connecting portion 13 as follows. When the raceway is deformed due to a bearing mounting failure, the rolling element 18 advances on the leading side with respect to the rotational direction in the state before the dropout shown in FIG. A delay of the rolling element 18 occurs at the end 11a) of the cage 11, and the advance delay of the rolling element 18 increases. In the state at the time of dropping shown in FIG. 4 (b), the rolling element 18 at the intermediate part becomes a fulcrum by the pulling force from the front side of the cage 11, and the rear end of the cage 11 is deformed into an arcuate shape. In the state after the drop-off shown in FIG. 4C, after the cage 11 is dropped, the rolling element 18 located at the rear end is further delayed from the pocket.

  According to the present invention, since the cage is an endless cage which is formed by connecting the segments in an annular shape and does not have a non-connecting portion in the circumferential direction, the bearing may be deformed, that is, the bearing may be deformed. The cage can be reliably prevented from falling out even if there is a bearing installation failure, such as when the bearing is in poor use, or when the bearing is designed internally, such as a special design with a four-point contact ball bearing with different left and right contact angles. Therefore, it is possible to provide a highly reliable ultra-thin type rolling bearing.

  Embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 shows a specific structural example of the ultra-thin type rolling bearing 6 assembled in the CT scanner device (see FIG. 5). As shown in FIG. 2, the main part of the bearing is composed of an inner ring 23, an outer ring 24, a rolling element 25, and a cage 21. The inner ring 23 has a track on the outer peripheral surface and the outer ring 24 has a track on the inner peripheral surface, and a plurality of rolling elements 25 are rotatably incorporated between the tracks of the inner and outer rings 23 and 24. The cage 21 is interposed between the inner and outer rings 23 and 24 and holds the rolling elements 25 at a predetermined interval in the circumferential direction. Normally, a seal is attached to seal the bearing space between the inner and outer rings 23 and 24 to prevent leakage of the lubricant and entry of foreign matter from the outside, but the illustration is omitted here.

  In this embodiment, a ball is illustrated as the rolling element 25, but rollers can also be used. Further, the present invention is not limited to a single row bearing in which the number of rows of rolling elements 25 is one row, but can also be applied to a double row bearing having two rows of rolling elements.

  As shown in FIG. 1, the cage 21 has an endless shape in which a plurality of arc-shaped segments 22 are connected in a ring shape and do not have the non-connecting portion 13 (see FIG. 6) in the circumferential direction. Each segment 22 is formed by injection molding a resin material into a predetermined shape, and as the resin material, the ambient temperature of the CT scanner bearing is normally about 60 to 80 ° C., so the adverse effect of this temperature change is suppressed. In addition, in order to suppress expansion due to water absorption, for example, PPS (polyphenylene sulfide) having a small linear expansion coefficient is suitable. In each segment 22, a plurality of pockets for accommodating the rolling elements 25 are formed at equal intervals in the circumferential direction. The pocket has a form in which one side in the axial direction is opened. Furthermore, the connection part for connecting adjacent segments is provided in the both ends of each segment 22. As shown in FIG. Note that the shape of the segment 22, the form of the pocket, the incorporation of the rolling elements 25 into the pocket, and the connecting portion structure of the segment 22 are the same as those described with reference to FIG.

  In the ultra-thin type rolling bearing incorporating the retainer 21, the outer ring 24 is fixed to the rotary mount 8 of the CT scanner device shown in FIG. 5 and the inner ring 23 is fixed to the fixed mount 7. In this case, the outer ring 24 is a rotating member that rotates together with the rotating mount 8, and the inner ring 23 is a non-rotating fixing member. However, depending on the structure of the CT scanner device, the outer ring 24 is fixed to the non-rotating fixed side, contrary to the above. The inner ring 23 may be a rotating side that rotates together with the rotating mount 8.

  The present applicant conducted a test assuming that the ultra-thin rolling bearing incorporating the cage 21 of this embodiment is mounted on a CT scanner device. FIG. 3 shows the mounting state of the bearing (specimen) at the time of the test assuming the state mounted on the CT scanner device. As shown in the figure, the outer ring 34 of the specimen is fixed to the base plate 41 with a bolt 43 through a spacer 42. The outer ring 34 is bolted at a plurality of locations (for example, eight locations at 45 ° intervals) at equal intervals in the circumferential direction. In addition, as the spacers 42, a plurality of types having different thicknesses are prepared, and the amount of local deformation in the outer ring 34 can be set by varying the thicknesses of the spacers 42 at the bolt fixing positions in the circumferential direction. It is possible.

  In this test, the inner ring 33 of the test specimen rotates smoothly if it is in a normal mounting state, but a very large deformation (here, assumed flatness of the base plate 41 at the bearing mounting section). In contrast, when the inner ring 33 is rotated by being attached with a deformation amount of 10 times or more, the advance delay of the rolling element 35 held by the cage 21 increases, and the conventional cage 11 shown in FIG. In the specimen used, the cage 11 dropped off. In contrast, in the specimen using the cage 21 of the embodiment shown in FIG. 1, the cage 21 did not fall off even if the advancement delay of the rolling element increased due to deformation of the specimen. . This ensures that the cage will not fall off due to disturbance from the periphery of the bearing (for example, a mounting failure of the bearing) or the design of the bearing (for example, a special design with a four-point contact ball bearing with different left and right contact angles). Is possible.

It is a front view showing an embodiment of a cage for ultra-thin type rolling bearing according to the present invention. It is principal part expanded sectional drawing which shows the state which integrated the holder | retainer of FIG. 1 in embodiment of the ultra-thin type rolling bearing which concerns on this invention. It is a fragmentary sectional view which shows the state which attached the bearing to the base plate through the spacer in the test supposing the state which mounted the ultra-thin form rolling bearing in the CT scanner apparatus. It is for demonstrating the mechanism in which the conventional holder | retainer falls, (a) is the state before dropping, (b) is the state at the time of dropping, (c) is a partial front view which shows the state after dropping, respectively. . It is sectional drawing which shows schematic structure of CT scan apparatus. It is a front view which shows the conventional cage for ultra-thin type rolling bearings. It is a front view which shows the segment which comprises the holder | retainer of FIG.

Explanation of symbols

21 Cage 22 Segment 23 Inner ring 24 Outer ring 25 Rolling element

Claims (5)

  A cage for an ultra-thin type rolling bearing composed of a plurality of arc-shaped segments, wherein the segments are connected in an annular shape and endless with no unconnected portion in the circumferential direction. Super thin rolling bearing cage.   The cage for an ultra-thin type rolling bearing according to claim 1, wherein the segment is made of resin.   The cage for an ultra-thin type rolling bearing according to claim 2, wherein the resin is PPS (polyphenylene sulfide).   A plurality of rolling elements incorporated between the races of the inner ring, outer ring, and inner and outer rings are provided, and the rolling elements are held at predetermined intervals in the circumferential direction by the cage according to any one of claims 1 to 3. Super thin wall rolling bearing.   5. The ultra-thin rolling device according to claim 4, wherein one of the outer ring and the inner ring is fixed to a rotating mount of a CT scanner device that rotates around a subject, and the other is fixed to a fixed mount of the CT scanner device. bearing.

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