Patent Application
20240077109
The present invention relates to a crown type cage for a ball bearing, and a ball bearing.
Generally, a ball bearing 1 as shown in
Each ball 6 is rotatably held by a cage 100. In addition, outer peripheral edges of a pair of circular ring-shaped shield plates 7 and 7 are respectively locked to both end portions of the inner peripheral surface of the outer ring 5 in the axial direction. The pair of shield plates 7 and 7 prevents lubricant such as grease existing in the bearing space from leaking to the outside and dust floating outside from entering the bearing space. As a sealing device, a contact type seal may be used instead of the non-contact type shield plates 7 and 7.
The cage 100 is a resin crown type cage, as shown in
The pillar portion 110 has a pair of claw portions 112 and 112 of which tip end portions are spaced apart from each other. The two adjacent claw portions 112 and 112 forming the pocket 111 hold the ball 6, thereby preventing the cage 100 from slipping out from between the outer ring 5 and the inner ring 3 in the axial direction.
Incidentally, with the recent electrification of automobiles, rolling bearings (especially ball bearings) that support the rotation shafts of motors are required to rotate at high speed. In order to achieve high-speed rotation, it is required that (i) the centrifugal force expansion of the cage is suppressed and the stress generated at the bottom portion of the pocket is reduced to prevent fatigue fracture, and (ii) the deformation of the cage is suppressed to avoid contact of the cage with the outer ring and the seal, and suppress wear, vibration, and heat generation of the cage.
In the cage 100 of the related art as shown in
Patent Literature 1 and Patent Literature 2 disclose techniques for reducing the weight of the cage.
Specifically, Patent Literature 1 discloses that a thinned portion is formed on the end surface of the crown type cage opposite to the end surface on the pocket forming portion side. This thinned portion improves the left-right mass balance in the axial direction of the crown type cage and reduces the weight of the back surface side part.
Further, the cage disclosed in Patent Literature 2 has an annular base portion and an axial portion extending in the axial direction from the base portion. The outer diameter of the axial portion is smaller than the outer diameter of the base portion. The base portion is formed with a hole that communicates with the recessed area of the axial portion and penetrates therethrough in the axial direction. Therefore, it is intended to reduce the amount of material and suppress deformation in the radial direction induced during high-speed rotation.
However, in order to adapt the bearing to higher speed rotation, it is necessary to further reduce the weight of the cage.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a crown type cage for a ball bearing and a ball bearing capable of suppressing deformation by reducing the centrifugal force during high-speed rotation by reducing weight.
The above objects of the present invention are achieved by the following configurations.
(1) A crown type cage for a ball bearing including:
(2) The crown type cage for a ball bearing according to (1), in which
(3) The crown type cage for a ball bearing according to (1) or (2), in which
(4) The crown type cage for a ball bearing according to (3), in which
(5) The crown type cage for a ball bearing according to any one of (1) to (4), in which
(6) The crown type cage for a ball bearing according to any one of (1) to (5), in which
in the two adjacent claw portions that form the pocket, a peripheral distance between the two second peripheral surfaces decreases from the main portion side toward the tip end portion side of the claw portion.
(7) A ball bearing including:
With the crown type cage for a ball bearing and a ball bearing of the present invention, the centrifugal force at the time of high-speed rotation can be reduced by weight reduction, and deformation can be suppressed.
A crown type cage for a ball bearing and a ball bearing according to one embodiment of the present invention will be described below with reference to the drawings.
As shown in
The crown type cage 10 is made of, for example, resin materials such as nylon 46 (polyamide 46, PA46), nylon 66 (polyamide 66, PA66), polyamide 9T (PA9T), polyamide 10T (PA10T), L-PPS, and PEEK, or another resin material. Further, in order to improve the strength of the cage 10, a resin composition to which several tens of percent (for example, 10 to 50% by weight) of a fiber-reinforced material (carbon fiber, glass fiber, aramid fiber, and the like) is added may be used. As a method for manufacturing the cage 10, a method of injection molding using a mold and a manufacturing method with a 3D printer are exemplified.
The crown type cage 10 includes an annular main portion 20, a plurality of pillar portions 30 protruding in the axial direction from an upper surface 21 of the main portion 20 at predetermined intervals in the peripheral direction, and a spherical pocket 40 formed between the adjacent pillar portions 30 and 30 and capable of holding the balls 6 (refer to
A plurality of spherical recessed surfaces 23 having a spherical shape are formed on the upper surface 21 of the main portion 20 at predetermined intervals in the peripheral direction. This spherical recessed surface 23 is formed over the entire radial width of the main portion 20 and forms the pocket 40.
The pillar portion 30 protrudes in the axial direction from the radially inner side portion of the upper surface 21 of the main portion 20. Therefore, the upper surface 21 of the main portion 20 is exposed on the radially outer side of the pillar portion 30. In the crown type cage 100 (refer to
The pillar portion 30 has a pair of claw portions 31 and 31 and a connection portion 33 that connects the pair of claw portions 31 and 31.
Tip end portions 31A and 31A of the pair of claw portions 31 and 31 are spaced apart from each other in the peripheral direction. In addition, between the tip end portions 31A and 31A of the two adjacent claw portions 31 and 31 forming the pocket 40, an inlet 41 having a width shorter than the diameter of the ball 6 (refer to
The claw portion 31 has a spherical first peripheral surface 31B forming the pocket 40 and a second peripheral surface 31C opposite to the first peripheral surface 31B.
The second peripheral surfaces 31C and 31C of the pair of claw portions 31 and 31 are curved, respectively, and smoothly connected to an upper surface 33A of the connection portion 33. The upper surface 33A of the connection portion 33 corresponds to a substantially U-shaped bottom portion formed by the pair of second peripheral surfaces 31C and 31C. The upper surface 33A of the connection portion 33 (the bottom portions of the pair of second peripheral surfaces 31C and 31C) is positioned slightly above (on one axial side) the upper surface 21 of the main portion 20 (refer to
The first peripheral surfaces 31B and 31B of the two adjacent claw portions 31 and 31 and the spherical recessed surface 23 of the main portion 20 form the pocket 40. These two first peripheral surfaces 31B and 31B and the spherical recessed surface 23 are smoothly connected to each other to form the spherical recessed surface of the pocket 40. The radius of curvature of the spherical recessed surface of pocket 40 is set larger than the radius of curvature of the rolling surface of the ball 6 (refer to
In this manner, since the plurality of pockets 40 are connected by the main portion 20, when a centrifugal force is applied to the cage 10 during high-speed rotation, the cage 10 tends to be tilted to the radially outer side around the main portion 20. In order to suppress this tilt, in the present application, the regions S1 and S2 are cut as described above.
F=mrω2 where F is the centrifugal force, m is the mass, r is the distance from a rotation shaft to a rotating object (the cage 10), and ω is the angular velocity. The stress σ generated in the cage 10 (especially the bottom portion of the pocket 40) and the deformation amount 6 of the cage 10 are approximately proportional to the centrifugal force F. Therefore, when the axial width of the ball bearing 1, the inner diameter of the inner ring 3, and the outer diameter of the outer ring 5 are constant, it is necessary to reduce the mass m of the cage 10 in order to reduce the stress a and the deformation amount 6. Further, since the deformation amount 6 of the cage 10 is substantially inversely proportional to the rigidity of the cage 10, when the shape of the cage 10 does not change, the rigidity of the cage 10, that is, the Young's modulus may be increased.
As shown in
Further, an axial width H1 (vertical width in
In addition, when the axial width H1 is made extremely small, since there is a possibility that the strength of the cage 10 decreases, the axial width H1 is preferably larger than an axial width H3 (refer to
Further, the main portion 20 is provided with an opening portion 27 which is open in the axial direction between adjacent pockets 40 and 40. The opening portion 27 penetrates the bottom surface 26 from the upper surface 21 of the main portion 20 in the axial direction. The opening portion 27 is positioned on the radially outer side of the pillar portion 30 (the pair of claw portions 31 and 31). That is, at least a part of the opening portion 27 overlaps the pillar portion 30 (the pair of claw portions 31 and 31) in the peripheral direction. Moreover, the claw portion 31 and the opening portion 27 are provided offset in the radial direction, and the opening portion 27 is positioned on the radially outer side of the claw portion 31. The shown peripheral wall portion of the opening portion 27 is composed of a stepped surface (refer to
When a radial width t3 (refer to
As described above, with the cage 10 of the present embodiment, D1<D2, t1≤(t2/2), and H1≤(H2/2) are satisfied, and the opening portions 27 are formed. Thus, the weight of the cage 10 is reduced, and deformation due to the centrifugal force during high-speed rotation can be suppressed. Therefore, the cage 10 can be prevented from coming into contact with the outer ring 5, the shield plate 7, and the like, and wear, vibration, and heat generation of the cage 10 can be suppressed. Moreover, the claw portion 31 and the opening portion 27 are provided offset in the radial direction, and the opening portion 27 is positioned on the radially outer side of the claw portion 31. As a result, the weight of the cage 10 can be reduced, the distance between the claw portions 31 and the outer ring 5 can be secured, and thus contact with the outer ring 5 can be suppressed even when the claw portions 31 are deformed. Further, since the claw portion 31 is shaped to hold the ball 6 from the radially inner side, in order for the claw portion 31 to deform when the centrifugal force acts, it is necessary to get over the ball 6, and there is also an effect of suppressing the deformation of the claw portion 31.
The projection portion 28 protrudes in the axial direction (a direction opposite to a direction in which the claw portion 31 extends in the vertical direction in
The projection portion 28 preferably overlaps the pocket 40 in the peripheral direction and the radial direction. That is, the peripheral range and the radial range in which the projection portion 28 is provided are preferably substantially the same as the peripheral range and the radial range in which the spherical recessed surface 23 of the main portion 20 forming the pocket 40 is provided. The radial width and peripheral width of the projection portion 28 of the present embodiment are substantially the same as the radial width (the radial width t2 of the main portion 20) and the peripheral width of the pocket 40.
With the cage 50 of the second embodiment, the effect of suppressing stress and deformation generated by the centrifugal force is not so different from that of the first embodiment, but the cage 50 is effective when the cage 50 is incorporated into the bearing 1 consisting of the inner ring 3, the outer ring 5, and the balls 6. That is, as will be described later, strain generated in the claw portions 31 of the cage 50 is reduced.
In the cage 60 of the present embodiment, the radial width of the claw portion 31 decreases from the main portion 20 side toward the tip end portion 31A of the claw portion 31. That is, the relationship among radial widths a1, a2, and a3 of the claw portion 31 in
With such a configuration, the stress and strain generated in the claw portion 31 can be reduced. In particular, this configuration is effective when the tip end portion 31A of the claw portion 31 receives force from the ball 6. Moreover, when the cage 60 is injection molded, the cage 60 can be easily removed from the mold, which is effective.
In the cage 70 of the present embodiment, in the two adjacent claw portions 31 and 31 forming the pocket 40, the peripheral distance between the two second peripheral surfaces 31C and 31C decreases from the main portion 20 side to the tip end portion 31A of the claw portion 31. That is, the relationship of the peripheral distances b1, b2, and b3 between the second peripheral surfaces 31C and 31C of the two adjacent claw portions 31 and 31 in
With such a configuration, the stress and strain generated in the claw portion 31 can be reduced. In particular, this configuration is effective when the tip end portion 31A of the claw portion 31 receives force from the ball 6. Moreover, when the cage 70 is injection molded, the cage 70 can be easily removed from the mold, which is effective.
In order to confirm the effects of the present invention, analysis was performed using the finite element method. The cages 10 and 50 to be analyzed are crown type resin cages used for bearings with an inner diameter of 35 mm. Based on the crown type resin cage of the related art, the shape was set based on the embodiment of the present invention. That is, as shown in
Regarding the cage size, both in Comparative Example and Examples 1 and 2, the inner diameter of the cages 10 and 50 (100) was set to 49 mm, the maximum outer diameter of the main portion 20 (109) was set to 58 mm, and the axial height of the cages 10 and 50 (100) was set to 10 mm. The axial width H1 from the upper surface 33A of the connection portion 33 of the pillar portion 30 (110) to the bottom surface 26 of the main portion 20 (109) was set to 7 mm in Comparative Example and 3 mm in Examples 1 and 2. In addition, the radial thickness of the tip end portion 31A of the claw portion 31 (112) was set to 4.7 mm in Comparative Example and 1.2 mm in Examples 1 and 2. The radial thickness of the opening portion 27 of the main portion 20 was set to 2 mm in Examples 1 and 2. The axial thickness of the projection portion 28 in Example 2 was set to 0.9 mm.
As the physical property values of the cages 10 and 50 (100), values corresponding to nylon 46 (PA46) at high temperatures were used, assuming that the bearings would be used in high-speed rotation. Specifically, Young's modulus was set to 3500 MPa, Poisson's ratio was set to 0.4, and density was set to 1.38 g/cm3. The rotation speed of the inner ring was 30,000 rpm.
The maximum principal stress distribution generated in the cages 10 and 50 (100) by the centrifugal force is shown in
In both Examples 1 and 2, the values of (i) to (iv) were greatly reduced compared to the related art, confirming the effect. There was almost no difference between Example 1 and Example 2 in (i) the stress of the pocket bottom, (ii) the radial displacement amount, and (iii) the axial displacement amount, but (iv) the strain at the time of ball incorporation in Example 2 was reduced by approximately 20% compared to that of Example 1.
It is considered that, this is because, as shown in
In the related art, the part near the tip end portion of the claw portion 112 tends to widen toward the fulcrum P, and thus the strain region (strain generation region D) generated in the claw portion 112 becomes narrower and the strain increases. On the other hand, in Example 1, since the distance from the tip end portion 31A of the claw portion 31 to the fulcrum P is long, the strain generation region D widens, and the strain is lower than in the related art. Furthermore, in Example 2, since the distance from the tip end portion 31A of the claw portion 31 to the fulcrum is long, the strain generation region D further widens, and the strain is further reduced than in Example 1.
It should be noted that the cages 10 and 50 of Examples 1 and 2 as described above are preferably applied to a cage using a resin material having a lower strain strength than nylon 46 or nylon 66 because strain can be reduced.
The present application is based on Japanese Patent Application No. 2021-005913 filed on Jan. 18, 2021, and the content thereof is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-005913 | Jan 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/001445 | 1/17/2022 | WO |
