Cage for rolling bearings and rolling bearings equipped therewith
The cage design with convex walls generates airflow to counter centrifugal force, maintaining grease within the bearing and ensuring uniform lubrication, resulting in high-quality rolling bearings with improved performance and longevity.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NTN CORP
- Filing Date
- 2024-12-26
- Publication Date
- 2026-07-08
AI Technical Summary
In grease-lubricated rolling bearings, as the rotational speed increases, centrifugal force causes the grease to move radially outward, reducing the amount available for internal lubrication, especially in the inner diameter region, leading to inadequate lubrication and cooling.
A cage for rolling bearings with convex wall portions on its outer surface that generate an airflow to suppress grease movement outward and evenly distribute grease, enhancing internal lubrication performance.
The cage design achieves high-quality rolling bearings with excellent internal lubrication, long life, low heat generation, and low noise by preventing grease migration and ensuring uniform grease distribution.
Smart Images
Figure 2026114249000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a rolling bearing cage for a rolling shaft and a rolling bearing provided with the same.
Background Art
[0002] For example, Patent Document 1 below describes a rolling bearing that can be used to rotatably support the main shaft of a machine tool such as a machining center or a grinding machine. During the operation of the rolling bearing, the inside of the bearing (the contact part between the bearing components) is lubricated by one lubrication method selected from known lubrication methods such as oil mist lubrication, air-oil lubrication, jet lubrication, and grease lubrication. However, lubrication methods that use lubricating oil such as oil mist lubrication have problems such as environmental load issues due to the large amount of lubricating oil used and high costs due to the need for auxiliary equipment. Therefore, even for rolling bearings that support the main shaft of a machine tool with a rotational speed ranging from several thousand to tens of thousands of revolutions per minute (rpm), grease lubrication, which does not have the above-mentioned problems, is often adopted as the internal lubrication method.
[0003] In Patent Document 1, a cylindrical roller bearing, which is cited as a specific example of a rolling bearing for supporting the main shaft of a machine tool, includes an annular cage that holds cylindrical rollers as rolling elements. This cage includes a pair of annular portions that are arranged opposite to each other with a space in the axial direction, and a plurality of column portions that are arranged with a space in the circumferential direction and connect the annular portions. A window-shaped pocket for accommodating and holding cylindrical rollers is formed between a pair of annular portions and two adjacent column portions.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] In grease-lubricated rolling bearings, as the rotational speed of the supported shaft (and the raceway ring fixed to it) increases, the grease sealed inside the bearing moves radially outward due to centrifugal force and eventually adheres to the inner diameter surface of the outer ring. In this case, there is a concern that the amount of grease contributing to internal lubrication of the bearing decreases, especially in the inner diameter region of the bearing's internal space, making it impossible to adequately lubricate and cool the inside of the bearing.
[0006] In view of the above circumstances, the present invention aims to provide a cage for rolling bearings that can suppress the amount of lubricant (grease) moving radially outward due to the influence of centrifugal force, thereby realizing a high-quality rolling bearing with excellent internal lubrication performance, long life, low heat generation, and low noise. [Means for solving the problem]
[0007] The present invention, devised to achieve the above objectives, A cage for a rolling bearing comprises a pair of annular sections arranged opposite each other with an axial gap between them, and a plurality of columnar sections arranged with a gap in the circumferential direction and extending axially to connect the two annular sections, with pockets for housing rolling elements formed between the pair of annular sections and two circumferentially adjacent columnar sections, Multiple convex walls are provided on the outer surface of each annular section at intervals in the circumferential direction. Each of the above-mentioned convex wall portions extends from the pocket-side end of the annular portion to the non-pocket-side end, and the angle that its centerline makes with respect to the axial direction is 0° or more and 60° or less.
[0008] According to the present invention, a cage having the above-described convex wall portions on the outer circumferential surfaces of both annular portions, when the cage rotates around the central axis in conjunction with the operation of a rolling bearing incorporating the cage, an airflow can be generated that flows from the outer diameter side of the cage into the pocket. Therefore, when the cage according to the present invention is incorporated into a rolling bearing that employs grease lubrication as its internal lubrication method, even if centrifugal force acts on the grease interposed inside the bearing as the rotational speed of the shaft to be supported increases, the above-described airflow can suppress the movement of grease toward the outer diameter side of the cage. Furthermore, the above-described airflow can also diffuse (disperse) the grease adhering to the outer surface (rolling surface) of the rolling elements, thereby lubricating the rolling surface of the rolling elements over a wide area.
[0009] If the holder according to the present invention is an injection-molded product of a resin material integrally having a pair of annular parts, a plurality of columnar parts, and a plurality of convex wall parts, then holders with complex shapes due to the addition of convex wall parts can be mass-produced inexpensively and with high precision.
[0010] The width dimension (wall thickness) of the convex wall portion is preferably uniform along the extending direction of the convex wall portion and within the range of 10% to 30% of the axial width (width dimension in the axial direction) of the annular portion.
[0011] Preferably, the height dimension of the convex wall portion is uniform along the direction of extension of the convex wall portion, and is 90% or less of the radial gap formed between the outer circumferential surface of the retainer (or its annular portion) and the inner circumferential surface of the outer ring of the rolling bearing.
[0012] In a rolling bearing comprising an inner ring and an outer ring, a plurality of rolling elements interposed between the raceway surfaces of the inner ring and the outer ring so as to be rotatable, a cage that holds the plurality of rolling elements at circumferential intervals, and grease filled in the annular space between the outer circumferential surface of the inner ring and the inner circumferential surface of the outer ring, if the cage according to the present invention is used as the cage, the above-mentioned effects that the cage according to the present invention can provide make it possible to realize a rolling bearing with excellent internal lubrication performance, quiet operation, and long life. [Effects of the Invention]
[0013] From the above, the present invention provides a cage for rolling bearings that can suppress the amount of lubricant (grease) moving radially outward due to the influence of centrifugal force. Therefore, by using such a cage as a component, it is possible to realize a high-quality rolling bearing with excellent internal lubrication performance, long life, low heat generation, and low noise. [Brief explanation of the drawing]
[0014] [Figure 1] This is a schematic longitudinal cross-sectional view of a rolling bearing including a cage according to one embodiment of the present invention. [Figure 2] This is a partially unfolded plan view of a retainer according to one embodiment of the present invention. [Figure 3] This is an overall perspective view of the retainer. [Figure 4] Figures (a) and (b) are both partial unfolded plan views of a modified retainer. [Modes for carrying out the invention]
[0015] Embodiments of the present invention will be described below with reference to the drawings. In the following description, "axial direction," "radial direction," and "circumferential direction" refer to the direction along the central axis of the bearing, the radial direction of the circle centered on the central axis, and the circumferential direction of the circle centered on the central axis, respectively. In Figure 1, etc., the "axial direction," "radial direction," and "circumferential direction" are indicated by arrows X, Y, and Z, respectively.
[0016] Figure 1 is a schematic longitudinal cross-sectional view of a rolling bearing 1 having a cage according to one embodiment of the present invention as a component; Figure 2 is a partially unfolded plan view of the cage shown in Figure 1, showing the cage with rolling elements (cylindrical rollers) housed in the pockets; Figure 3 is a partially enlarged view of Figure 2; and Figures 4(a) and 4(b) are partially unfolded plan views of a modified cage.
[0017] The rolling bearing 1 of the present embodiment shown in FIG. 1 includes an inner ring 2 and an outer ring 3 that are coaxially arranged so as to be relatively rotatable, a plurality of cylindrical rollers 4 disposed between the inner ring 2 and the outer ring 3, and a cage 5 that holds the plurality of cylindrical rollers 4. Although not shown, the annular space between the inner ring 2 and the outer ring 3 is filled with grease for internal lubrication of the rolling bearing 1.
[0018] The rolling bearing 1 is used, for example, as a bearing for supporting the spindle of a machine tool such as a machining center. In this case, the inner ring 2 is mounted on the outer periphery of the spindle S that rotates around the central axis, and the outer ring 3 is mounted on the inner periphery of a stationary member such as a housing (not shown). From the above, the rolling bearing 1 of the present embodiment can also be said to be an inner ring rotation type cylindrical roller bearing with an internal lubrication method of grease lubrication.
[0019] A cylindrical inner raceway surface 2a is provided on the outer peripheral surface of the inner ring 2, and flange portions 2b that project radially outward are provided on both axial sides of the inner raceway surface 2a. By sandwiching the cylindrical rollers 4 between the pair of flange portions 2b from both axial sides, the dropout of the cylindrical rollers 4 from the rolling bearing 1 is prevented as much as possible. However, in order to prevent the presence of the pair of flange portions 2b from adversely affecting the rolling performance (operability) of the cylindrical rollers 4, a slight axial gap exists between the flange portions 2b and the cylindrical rollers 4.
[0020] A cylindrical outer raceway surface 3a that faces the inner raceway surface 2a of the inner ring 2 is provided on the inner peripheral surface of the outer ring 3. A plurality of cylindrical rollers 4 are disposed so as to be freely rotatable between the inner raceway surface 2a and the outer raceway surface 3a that face each other, and the cage 5 holds the plurality of cylindrical rollers 4 disposed between the two raceway surfaces 2a and 3a at intervals in the circumferential direction.
[0021] As also shown in FIG. 2, the cage 5 includes a pair of annular portions 6, 6 arranged to face each other with an axial spacing, and a plurality of column portions 7 arranged with a circumferential spacing and connecting the two annular portions 6. A rectangular pocket 8 for individually accommodating the cylindrical roller 4 is formed between the pair of annular portions 6, 6 and two column portions 7 adjacent to each other in the circumferential direction. On the pocket forming surface (the end face on the inner side in the axial direction) 6a of the annular portion 6 that forms the pocket 8, a convex portion 9 protruding into the pocket 8 is provided.
[0022] On the outer peripheral surfaces 6c of the one and the other annular portions 6, as shown in FIGS. 1 to 3, a plurality of convex wall portions 10 protruding radially outward are provided with a circumferential spacing.
[0023] The circumferential arrangement positions of the convex wall portions 10 (10A) provided on one annular portion 6 and the circumferential arrangement positions of the convex wall portions 10 (10B) provided on the other annular portion 6 coincide with each other, and each convex wall portion 10 (10A, 10B) is provided so that the whole is within the range of the circumferential width R of the pocket 8.
[0024] The convex wall portions 10 (10A, 10B) extend from the pocket side end portion 6a of the annular portion 6 to the anti-pocket side end portion 6b. That is, the axial position of the pocket side end portion 10a of the convex wall portion 10 coincides with the axial position of the pocket side end portion 6a of the annular portion 6, and the axial position of the anti-pocket side end portion 10b of the convex wall portion 10 coincides with the axial position of the anti-pocket side end portion 6b of the annular portion 6.
[0025] Each of the convex wall portions 10A, 10B of the present embodiment is provided such that its center line is inclined by an angle θ (= 40°) with respect to the axial direction, and the inclination directions are opposite to each other. As shown in FIG. 2, when the cage 5 rotates upward on the paper surface during the operation of the rolling bearing 1, each of the convex wall portions 10 (10A, 10B) is provided such that the anti-pocket side end portion 10b is located on the front side in the rotation direction from the pocket side end portion 10a.
[0026] To summarize, in this embodiment, the convex wall portion 10(10A) of one annular portion 6 is provided so as to be symmetrical with the convex wall portion 10(10B) of the other annular portion 6, with respect to the line that bisects the retainer 5 in the axial direction.
[0027] As the rolling bearing 1 operates (the spindle S rotates), the cage 5 of this embodiment, which has the convex wall portion 10 provided on the outer circumferential surface 6c of the annular portion 6, rotates so that the end 10b on the side opposite to the pocket of the convex wall portion 10 is located further forward in the rotational direction than the end 10a on the pocket side, as shown in Figure 2. In this case, the convex wall portion 10 can generate an airflow that flows from the outer diameter side of the cage 5 into the pocket 8. Therefore, when the cage 5 of this embodiment is incorporated into the rolling bearing 1 shown in Figure 1, which employs grease lubrication as the internal lubrication method, even if centrifugal force acts on the grease interposed in the annular space between the inner and outer rings as the rotational speed of the spindle S increases, the airflow can suppress the movement of grease toward the outer diameter side of the cage 5. Furthermore, the airflow can diffuse the grease adhering to the outer circumferential rolling surface of the cylindrical roller 4, allowing the rolling surface of the cylindrical roller 4 to be lubricated evenly over a wide area. Therefore, according to the cage 5 of this embodiment, a high-quality rolling bearing 1 can be realized that has excellent internal lubrication performance, long lifespan, low heat generation, and low noise.
[0028] In particular, in this embodiment, the convex wall portion 10 is provided such that the entire convex wall portion 10 is contained within the circumferential width R of the pocket 8, and the pocket-side end portion 10a of each convex wall portion 10 is positioned in the circumferential center of the pocket 8, thereby effectively enjoying the effects and advantages of the present invention described above.
[0029] In this embodiment, the retainer 5, which has a convex wall portion 10 on the outer circumferential surface 6c of a pair of annular portions 6, is structurally more complex than conventional retainers that do not have a portion corresponding to the convex wall portion 10, raising concerns about increased costs. Therefore, the retainer 5 is made of resin injection molded product in which the pair of annular portions 6, a plurality of column portions 7, a convex portion 9, and a projection 10 are integrated. This makes it possible to mass-produce a retainer 5 with a high-precision convex wall portion 10 at low cost.
[0030] Furthermore, as the resin material for molding the retainer 5, for example, a thermoplastic resin such as polyether ether ketone (PEEK), polyamide (PA, PA66, PA46, etc.), or polyphenylene sulfide (PPS) can be used as the main component, to which various fillers such as glass fiber (GF) or carbon fiber (CF) can be appropriately blended. The proportion of fillers in the total resin material can be, for example, 20 to 40% by mass.
[0031] As shown in an enlarged view in Figure 3, the width dimension (wall thickness) t of the convex wall portion 10 is made uniform along the extending direction of the convex wall portion 10 and set within a range of 10% to 30% of the axial width W of the annular portion 6. This is because if the wall thickness t of the convex wall portion 10 is too small (t < 0.1W), the above-mentioned effects may not be achieved due to insufficient rigidity of the convex wall portion 10, and if the wall thickness t of the convex wall portion 10 is too large (t > 0.3W), the volume of the convex wall portion 10 (and the retainer 5 on which it is provided) will increase, leading to higher costs for the retainer 5 and, consequently, the rolling bearing 1.
[0032] Furthermore, as shown in Figure 1, the height dimension h of the convex wall portion 10 is uniform along the direction of extension of the convex wall portion 10, and is 90% or less of the radial gap H formed between the outer circumferential surface of the cage 5 (outer circumferential surface 6c of the annular portion 6) and the inner circumferential surface 3a of the opposing outer ring 3. This is because if the height dimension h of the convex wall portion 10 exceeds 90% of the above gap H (h > 0.9H), the convex wall portion 10 will come into contact with the inner circumferential surface 3a of the outer ring 3 during bearing operation, and the convex wall portion 10 is likely to cause abnormal noise and rotational resistance. However, if the height dimension h of the convex wall portion 10 is too low, there is a concern that the above effects of providing the convex wall portion 10 cannot be fully enjoyed. For this reason, it is preferable that the height dimension h of the convex wall portion 10 be 60% or more of the above gap H.
[0033] The above describes a cage 5 according to one embodiment of the present invention and a rolling bearing 1 including the cage as a component, but the embodiments of the present invention are not limited thereto.
[0034] For example, in the embodiment described above, the convex wall portion 10 provided on the outer peripheral surface 6c of the annular portion 6 of the retainer 5 has an angle θ of 40° between its center line and the axial direction. However, this angle θ can be appropriately changed as long as it is within the range of 0° or more as shown in Figure 4(a) and 60° or less as shown in Figure 4(b). The reason for setting the lower limit of the angle θ to 0° is that if the angle θ is less than 0°, it is not possible to generate an airflow that flows into the pocket 8 when the retainer 5 rotates. The reason for setting the upper limit of the angle θ to 60° is that if the angle θ is greater than 60°, there is a concern that the amount of airflow that flows into the pocket 8 when the retainer 5 rotates will decrease as the distance between two adjacent convex wall portions 10 in the circumferential direction becomes narrower.
[0035] Furthermore, in the embodiments described above, the convex wall portion 10 is provided on the outer circumferential surface 6c of each annular portion 6 so that the entirety of one convex wall portion 10 fits within the circumferential range R of the pocket 8. However, it is also possible to provide the convex wall portion 10 on the outer circumferential surface 6c of each annular portion 6 so that the entirety of two or more convex wall portions 10 fits within the circumferential range R of the pocket 8. In addition, as long as the end portion 10a on the pocket side of each convex wall portion 10 is located on the pocket forming surface 6a (located within the circumferential range R of the pocket 8), the end portion 10b on the opposite side of the pocket may be located outside the circumferential range R of the pocket 8.
[0036] The above describes the case in which the cage 5 according to the embodiment of the present invention is used as a cage for a cylindrical roller bearing. However, the present invention can also be applied to cages for rolling bearings other than cylindrical roller bearings (for example, needle roller bearings, spherical roller bearings, ball bearings, etc.). [Explanation of Symbols]
[0037] 1. Rolling bearings (cylindrical roller bearings) 2 Inner ring 2a Inner raceway surface 3 Outer ring 3a Outer raceway surface 4 cylindrical rollers 5 Cage 6. Ring section 6a Pocket side end 6b End on the side opposite the pocket 7 Pillar part 8 pockets 10 Convex wall section 10a Pocket side end 10b End on the side opposite the pocket h Height dimension of the convex wall section t Width dimension of the convex wall S spindle Axial width of the annular section W θ angle
Claims
1. A cage for a rolling bearing comprising a pair of annular portions arranged opposite each other with an axial gap between them, and a plurality of columnar portions arranged with a gap in the circumferential direction and extending axially to connect the two annular portions, wherein a pocket for housing rolling elements is formed between the pair of annular portions and two of the columnar portions adjacent to each other in the circumferential direction, Multiple convex walls are provided on the outer surface of each annular section at intervals in the circumferential direction. The cage for a rolling bearing is characterized in that the convex wall portion extends from the pocket-side end of the annular portion to the non-pocket-side end, and the angle that its centerline makes with respect to the axial direction is 0° or more and 60° or less.
2. The rolling bearing cage according to claim 1, which is an injection-molded product of a resin material integrally having the pair of annular portions, the plurality of columnar portions, and the plurality of convex wall portions.
3. The rolling bearing cage according to claim 1, wherein the width dimension of the convex wall portion is uniform along the extending direction of the convex wall portion and within the range of 10% to 30% of the axial width of the annular portion.
4. A cage for a rolling bearing according to claim 1, wherein the height dimension of the convex wall portion is uniform along the extending direction of the convex wall portion, and the outer peripheral surface of the cage is 90% or less of the radial gap formed between it and the inner peripheral surface of the outer ring of the rolling bearing.
5. A rolling bearing comprising an inner ring and an outer ring, a plurality of rolling elements interposed between the raceway surfaces of the inner ring and the outer ring so as to be rotatable, a cage that holds the plurality of rolling elements at intervals in the circumferential direction, and grease filled in the annular space between the outer circumferential surface of the inner ring and the inner circumferential surface of the outer ring, wherein the cage is a rolling bearing cage according to any one of claims 1 to 4.