CN112412985B

CN112412985B - Retainer and bearing

Info

Publication number: CN112412985B
Application number: CN201910769996.5A
Authority: CN
Inventors: 罗堉玮; 陈秉杰
Original assignee: Hiwin Technologies Corp
Current assignee: Hiwin Technologies Corp
Priority date: 2019-08-20
Filing date: 2019-08-20
Publication date: 2022-09-02
Anticipated expiration: 2039-08-20
Also published as: CN112412985A

Abstract

The invention provides a retainer for a bearing. The retainer is of an annular structure and comprises a body part and a flange part. The body part defines a central axis and comprises a first surface, a second surface, a plurality of holes and at least one oil storage tank, wherein the second surface is opposite to the first surface, each hole is used for accommodating a rolling element, the oil storage tank is formed by sinking from the first surface and/or the second surface, the oil storage tank is positioned between two adjacent holes of the plurality of holes and is communicated with the two adjacent holes, the flange part is arranged on the outer periphery of the body part and comprises a first protruding part and a second protruding part, the first protruding part is adjacent to the first surface and protrudes outwards relative to the first surface to form a first height difference, and the second protruding part is adjacent to the second surface and protrudes outwards relative to the second surface to form a second height difference.

Description

Retainer and bearing

Technical Field

The present invention relates to a retainer and a bearing, and more particularly, to a retainer and a bearing which are advantageous for preventing leakage of a lubricant inside the bearing.

Background

The bearing is an important part in modern mechanical equipment, and the main function of the bearing is to support a mechanical rotating body, reduce the friction coefficient in the movement process of the mechanical rotating body and ensure the rotation precision of the mechanical rotating body.

In order to improve the lubricating effect, lubricating liquid is injected into some bearings so as to effectively reduce the friction coefficient and prolong the service life of the bearings. The structure of the retainer in the bearing is critical to the oil storage capacity and the lubrication effect of the bearing, and therefore, the related manufacturers are not dedicated to the improvement of the structure of the retainer.

In japanese patent application publication No. JP2001041250A, for example, a cage is disclosed, in which an inner wall surface of the cage includes a plurality of grooves for accommodating a lubricating liquid and a plurality of protrusions (elements shown by reference numerals 61 and 62 in fig. 11) for holding an axial position of a roller. However, the retainer has no structure for preventing the leakage of the lubricant, the lubricant inside the retainer gradually runs off along with the operation of the bearing to cause the failure of the lubricant, in addition, the structure of the retainer is not favorable for the circulation of the lubricant in the groove among different holes and the distribution uniformity of the lubricant, and the retainer is provided with protruding parts at the upper opening and the lower opening of the holes, thereby causing the difficulty of demoulding and reducing the qualification rate of the retainer.

Further, as an example, japanese patent application publication No. JP2008223919A discloses a cage in which an inner wall surface of the cage includes a plurality of projections (elements shown by reference numerals 16a and 16b in fig. 6) for holding an axial position of a roller. However, the structure of the retainer has a poor effect of preventing the leakage of the lubricant, and the retainer has protrusions at both the upper and lower openings of the hole, which also causes difficulty in demolding and reduces the yield of the retainer.

Disclosure of Invention

Therefore, it is an object of the related art to develop a new retainer that provides better lubrication and more preferably reduces the difficulty of mold release.

In order to achieve the purpose, the invention adopts the technical scheme that:

a retainer for a bearing, the retainer having an annular configuration, comprising:

a body portion defining a central axis, the body portion comprising:

a first surface;

a second surface opposite to the first surface, the second surface and the first surface having a spacing distance in a direction parallel to the central axis;

a plurality of holes, each hole penetrating through the body portion and communicating the first surface and the second surface, each hole for accommodating a rolling element; and

at least one oil storage groove formed by the first surface and/or the second surface in a concave mode, wherein the oil storage groove is located between two adjacent holes of the plurality of holes and is communicated with the two adjacent holes; and

a flange portion disposed at an outer periphery of the main body portion, the flange portion comprising:

a first protrusion adjacent to the first surface, the first protrusion protruding outward relative to the first surface to have a first height difference; and

and the second protrusion is adjacent to the second surface and protrudes outwards relative to the second surface to form a second height difference.

The retainer of the invention can reduce the clearance between the flange part and other parts of the bearing (such as the first annular structure and the second annular structure) by arranging the flange part on the outer periphery of the body part, thereby effectively preventing the lubricating liquid in the bearing from leaking outside, further being beneficial to maintaining the lubricating effect of the bearing and prolonging the service life of the bearing. The oil storage groove is communicated with two adjacent holes, so that the distribution uniformity of the lubricating liquid is facilitated.

According to the above-mentioned retainer, each of the holes may include a first opening and a second opening, wherein the first opening is disposed on the first surface of the body portion, the second opening is disposed on the second surface of the body portion, and each of the holes has a scoop-shaped structure disposed at the first opening or the second opening, the scoop-shaped structure being formed by two arc-shaped inner walls adjacent to the first opening or the second opening. So, be favorable to bearing the rolling member, and can avoid the first opening in hole and second opening to contain the spoon form structure simultaneously, be difficult for installing the rolling member and be difficult for the disappearance of drawing of patterns.

According to the above-mentioned retainer, the plurality of holes may include a plurality of first holes and a plurality of second holes, each of the first holes is provided with a spoon-shaped structure at the first opening, and each of the second holes is provided with a spoon-shaped structure at the second opening. Thus, the friction between the retainer and other components (such as the first annular structure and the second annular structure) when only the first hole or only the second hole is included can be avoided.

According to the above-mentioned retainer, the plurality of first holes or the plurality of second holes can be disposed at equal angles. In this way, it is beneficial to maintain the consistency of the spacing between the retainer and other components (such as the first annular structure and the second annular structure).

According to the above-mentioned retainer, the material of the retainer can be plastic. Thus, the weight reduction of the retainer is facilitated.

The present invention also provides a bearing, comprising:

a first ring structure;

a second annular structure;

the retainer is arranged between the first annular structure and the second annular structure, a first top edge of the first protruding part of the flange part is adjacent to an inner surface of the first annular structure, and a second top edge of the second protruding part of the flange part is adjacent to an inner surface of the second annular structure; and

the rolling pieces are correspondingly arranged in the holes of the retainer.

The bearing, wherein: the first top edge and the first annular structure have a first gap distance, the second top edge and the second annular structure have a second gap distance, and the sum of the first gap distance and the second gap distance is 0.1mm to 0.4 mm.

The bearing of, wherein: the first annular structure includes a first annular protrusion disposed on the inner surface of the first annular structure, the second annular structure includes a second annular protrusion disposed on the inner surface of the second annular structure, the first annular protrusion and the second annular protrusion are adjacent to form a shaft, each rolling element is a first rolling element, and the bearing further includes:

a third annular structure disposed between the first annular structure and the second annular structure and surrounding the shaft portion; and

a plurality of second rolling elements arranged between the shaft part and the third annular structure;

the number of the retainers is two, and the retainers are respectively a first retainer and a second retainer, the first retainer is arranged between the first annular structure and the third annular structure and surrounds the shaft part, and the second retainer is arranged between the third annular structure and the second annular structure and surrounds the shaft part.

According to another embodiment of the present invention, a bearing is provided, which includes a first annular structure, a second annular structure, the retainer and a plurality of rolling elements, wherein the retainer is disposed between the first annular structure and the second annular structure, a first top edge of a first protrusion of the flange portion is adjacent to an inner surface of the first annular structure, a second top edge of a second protrusion of the flange portion is adjacent to an inner surface of the second annular structure, and the rolling elements are disposed corresponding to the holes of the retainer. The bearing provided by the invention can effectively prevent the lubricating liquid in the bearing from leaking outside and can improve the uniformity of the distribution of the lubricating liquid by comprising the retainer.

According to the above-mentioned bearing, the first top edge and the first annular structure may have a first gap distance, the second top edge and the second annular structure may have a second gap distance, and the sum of the first gap distance and the second gap distance may be 0.1mm to 0.4 mm. Therefore, the effect of preventing the lubricating liquid from leaking can be further improved, and mutual friction among the first annular structure, the second annular structure and the retainer can be avoided.

According to the above-mentioned bearing, the first annular structure may include a first annular protrusion disposed on an inner surface of the first annular structure, the second annular structure may include a second annular protrusion disposed on an inner surface of the second annular structure, the first annular protrusion and the second annular protrusion are adjacent to form a shaft, and each rolling element is a first rolling element. The bearing may further include a third annular structure disposed between the first and second annular structures and surrounding the shaft portion, and a plurality of second rolling elements disposed between the shaft portion and the third annular structure. The number of the retainers is two, and the retainers are respectively a first retainer and a second retainer, the first retainer is arranged between the first annular structure and the third annular structure and surrounds the shaft part, and the second retainer is arranged between the third annular structure and the second annular structure and surrounds the shaft part. By means of the arrangement of the first rolling part and the second rolling part, the bearing capacity of the bearing in the radial direction and the axial direction can be improved.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 is a perspective view of a holder according to an embodiment of the present invention.

Fig. 2 is a schematic plan view of the holder of fig. 1.

Fig. 3 is a schematic partial cross-sectional view of the holder of fig. 2 taken along secant line a-a.

Fig. 4 is an enlarged schematic view of the X-point in fig. 2.

FIG. 5 is a schematic cross-sectional view of the region X in FIG. 4 along section line B-B.

FIG. 6 is a schematic cross-sectional view taken along section line C-C at location X in FIG. 4.

Fig. 7 is a schematic cross-sectional view of the Y-site in fig. 2.

Figure 8 is a schematic view of the holder of figure 1 for holding the rolling elements.

FIG. 9 is a schematic cross-sectional view of a bearing according to another embodiment of the present invention.

Fig. 10 is a perspective view of a bearing according to another embodiment of the present invention.

Fig. 11 is an exploded view of the bearing of fig. 10.

FIG. 12 is a schematic cross-sectional view of the bearing of FIG. 10 taken along section line D-D.

Description of reference numerals: 10-a first component; 20-a second component; 30. 400-rolling elements; 100-a holder; 100 a-a first holder; 100 b-a second holder; 120-a body portion; 130-flange portion; 131-a first protrusion; 132-a second protrusion; 133-first top edge; 134-a second top edge; 140-a first hole; 141. 151-a first opening; 142. 152-a second opening; 143. 153-spoon-like structure; 144. 145, 154, 155-arc inner wall; 150-second holes; 160-a first surface; 170-a second surface; 180-oil storage tank; 200. 500-a first cyclic structure; 210. 310, 510, 610-inner surface; 300. 600-a second ring structure; 520-a first loop portion; 521-first step; 522-second step; 620-second annular protrusion; 700-a shaft portion; 710-space; 800-a third cyclic structure; 900-a first rolling member; 950 — a second rolling member; 1000. 2000-bearing; d 1-separation distance; d 2-thickness; d3, d 4-spacing; d 5-first gap distance; d 6-second gap distance; r 1-diameter; r2, r 3-outer diameter; h1 — first height difference; h2 — second height difference; o-central axis; x, Y-part.

Detailed Description

Referring to fig. 1 to 3, fig. 1 is a schematic perspective view of a holder 100 according to an embodiment of the present invention, fig. 2 is a schematic plan view of the holder 100 in fig. 1, fig. 2 illustrates one surface of the holder 100, and the other surface of the holder 100 is configured the same as the aforementioned surface, fig. 3 is a schematic partial cross-sectional view of the holder 100 in fig. 2 along a secant line a-a, the schematic cross-sectional view of the holder 100 along the secant line a-a is left-right symmetrical, and a right half portion is omitted. The retainer 100 is used for a bearing (not shown), the retainer 100 is a ring structure and includes a body portion 120 and a flange portion 130, the body portion 120 defines a central axis O, the body portion 120 includes a first surface 160, a second surface 170, a plurality of holes, and at least one oil reservoir 180. The second surface 170 is opposite to the first surface 160, and the second surface 170 and the first surface 160 have a spacing distance d1 in a direction parallel to the central axis O. The plurality of holes are respectively a plurality of first holes 140 and a plurality of second holes 150. Each of the first holes 140 and each of the second holes 150 penetrate through the body 120 to communicate with the first surface 160 and the second surface 170, and each of the first holes 140 and each of the second holes 150 are used for accommodating a roller (not shown), and if the holes are not specifically referred to as the first holes 140 or the second holes 150, the holes may be the first holes 140 or the second holes 150. In fig. 2, the hole is elongated and can be used to accommodate the roller, however, the shape of the hole can be adjusted according to the shape of the rolling element, for example, the rolling element can also be a ball, and the hole can also be configured to be circular.

The flange 130 is disposed at an outer periphery (not shown) of the main body 120, the flange 130 includes a first protrusion 131 and a second protrusion 132, the first protrusion 131 is adjacent to the first surface 160, the first protrusion 131 protrudes outward relative to the first surface 160 to have a first height difference H1, in particular, a first top edge 133 of the first protrusion 131 has a first height difference H1 with the first surface 160, the second protrusion 132 is adjacent to the second surface 170, the second protrusion 132 protrudes outward relative to the second surface 170 to have a second height difference H2, in particular, a second top edge 134 of the second protrusion 132 has a second height difference H2 with the second surface 170. In other words, the thickness d2 of the flange portion 130 along the central axis O is greater than the thickness of the body portion 120 along the central axis O (i.e., the distance d1 separating the second surface 170 from the first surface 160 in a direction parallel to the central axis O). Thus, the lubricating liquid can be effectively prevented from leaking outwards. In addition, in the present embodiment, the first height difference H1 is equal to the second height difference H2. However, the invention is not limited thereto, and in other embodiments, the first height difference H1 may be different from the second height difference H2, depending on the actual requirement.

Referring to fig. 4 to 6 together, fig. 4 is an enlarged schematic view of a portion X in fig. 2, fig. 5 is a schematic cross-sectional view of the portion X in fig. 4 along a section line B-B, and fig. 6 is a schematic cross-sectional view of the portion X in fig. 4 along a section line C-C. The first hole 140 includes a first opening 141 and a second opening 142, the first opening 141 is disposed on the first surface 160 of the body 120, the second opening 142 is disposed on the second surface 170 of the body 120, the first hole 140 is disposed with a scoop-shaped structure 143 at the first opening 141, the scoop-shaped structure 143 is formed by arc-shaped

inner walls

144, 145 adjacent to the first opening 141, and in detail, the arc-shaped

inner walls

144, 145 are retracted inward to form the scoop-shaped structure 143, so that the size of the first opening 141 is smaller than the diameter of the rolling member to support the rolling member. Please refer to fig. 7, which is a schematic cross-sectional view of the portion Y in fig. 2. The second hole 150 includes a first opening 151 and a second opening 152, the first opening 151 is disposed on the first surface 160 of the body 120, the second opening 152 is disposed on the second surface 170 of the body 120, the second hole 150 is disposed with a scoop-shaped structure 153 at the second opening 152, the scoop-shaped structure 153 is formed by arc-shaped inner walls 154 and 155 adjacent to the second opening 152. The material of the retainer 100 may be plastic, such as thermoplastic, which may be, but not limited to, Polyimide (PI) resin or Polyetheretherketone (PEEK) resin, which is advantageous for reducing the weight of the retainer 100 compared to metal material. In addition, the retainer 100 may be manufactured by injection molding, and the mating holes (140, 150) include only a single scoop-shaped structure (143, 153), which facilitates demolding of the retainer 100 and increases manufacturability of the retainer 100.

Referring to fig. 8 and 5, fig. 8 and a schematic view of the retainer 100 in fig. 1 for fixing the rolling element 30, when the retainer 100 is installed between the first member 10 and the second member 20 of the bearing, the rolling element 30 is disposed in the first hole 140, the first member 10 has a distance d3 from the first surface 160 of the retainer 100, the second member 20 has a distance d4 from the second surface 170 of the retainer 100, if the retainer 100 is only provided with the first hole 140, since the size of the second opening 142 is larger than the diameter of the rolling element 30, the rolling element 30 is pressed by the first member 10 to move downward, which results in the distance d3 being reduced to generate friction between the retainer 100 and the first member 10, and similarly, if the retainer 100 is only provided with the second hole 150, it is not beneficial to maintain the size of the distance d 4. Therefore, the retainer 100 of the present invention includes both the first hole 140 and the second hole 150, which is advantageous to maintain the distance (e.g., d3, d4) between the retainer 100 and other components, so as to avoid friction between the retainer 100 and the first component 10 or the second component 20. In this embodiment, the number of the second holes 150 is three, as indicated in fig. 1 and 2, and the remaining holes are the first holes 140, wherein the second holes 150 are disposed at equal angles, i.e. the included angle between two second holes 150 is 120 degrees, however, the invention is not limited thereto, for example, in other embodiments, the number of the second holes 150 may be two, and the included angle between two adjacent second holes 150 may be 180 degrees, so that the equal angle disposition is favorable for maintaining the consistency of the spacing (e.g. d3, d4) between the holder 100 and other components.

Referring to fig. 1, 2 and 6, the main body 120 may further include a plurality of oil storage grooves 180, the oil storage grooves 180 are disposed on the first surface 160 and the second surface 170 of the main body 120, and are formed by the first surface 160 and the second surface 170 being recessed and configured in a cross shape, the oil storage groove 180 is located between two adjacent holes, and the oil storage groove 180 is communicated with the two adjacent holes, so that the flow of the lubricant between different holes is facilitated, and the uniformity of the distribution of the lubricant is facilitated. In other embodiments, the oil storage groove 180 may be disposed only on the first surface 160 or the second surface 170 of the body portion 120, and the number of the oil storage grooves 180 may be only one, so that the amount of the lubricating fluid in the bearing may be increased by disposing the oil storage groove 180.

Fig. 9 is a schematic cross-sectional view of a bearing 1000 according to another embodiment of the present invention. The bearing 1000 includes a first ring structure 200, a second ring structure 300, a retainer 100 and a plurality of rolling members 400, wherein the retainer 100 is disposed between the first ring structure 200 and the second ring structure 300, the rolling members 400 are correspondingly disposed in the holes of the retainer 100, and the rolling members 400 on the left side are omitted for clarity of the retainer 100. The first top edge 133 of the first protrusion 131 of the flange portion 130 is adjacent to the inner surface 210 of the first ring structure 200, the first top edge 133 has a first gap distance d5 from the inner surface 210, the second top edge 134 of the second protrusion 132 of the flange portion 130 is adjacent to the inner surface 310 of the second ring structure 300, the second top edge 134 has a second gap distance d6 from the inner surface 310, and the sum (d5+ d6) of the first gap distance d5 and the second gap distance d6 is 0.1mm to 0.4 mm. Thus, the effect of preventing the lubricant from leaking out can be further enhanced, and the first annular structure 200, the second annular structure 300, and the retainer 100 can be prevented from rubbing against each other. The size of the roller 400 can be flexibly adjusted according to the requirement of the device, as shown in the right side of fig. 9, the sum of the first gap distance d5 and the second gap distance d6 is the difference between the diameter r1 of the roller 400 and the thickness d2 of the flange 130 along the central axis O.

Referring to fig. 10 to 12, fig. 10 is a perspective view of a bearing 2000 according to another embodiment of the present invention, fig. 11 is an exploded view of the bearing 2000 of fig. 10, and fig. 12 is a cross-sectional view of the bearing 2000 of fig. 10 along a section line D-D. The bearing 2000 includes a first ring structure 500, a second ring structure 600, a third ring structure 800, a first holder 100a, a second holder 100b, a plurality of first rolling members 900 and a plurality of second rolling members 950, and the first rolling members 900 and the second rolling members 950 are omitted in fig. 12 for clarity of showing the relationship among the other elements. The bearing 2000 may be a slewing bearing (RTB). The bearing 2000 is provided with the first rolling element 900 and the second rolling element 950 at the same time, which is beneficial to improving the bearing capacity of the bearing 2000 in the radial direction and the axial direction.

The first ring structure 500 includes a first annular protrusion 520 disposed on the inner surface 510 of the first ring structure 500, the second ring structure 600 includes a second annular protrusion 620 disposed on the inner surface 610 of the second ring structure 600, the first annular protrusion 520 and the second annular protrusion 620 are adjacent to form a shaft 700, the third ring structure 800 is disposed between the first ring structure 500 and the second ring structure 600 and surrounds the shaft 700, the first retainer 100a is disposed between the first ring structure 500 and the third ring structure 800 and surrounds the shaft 700, the second retainer 100b is disposed between the third ring structure 800 and the second ring structure 600 and surrounds the shaft 700, and the first rolling element 900 is disposed in a hole (not numbered) of the first retainer 100a and the second retainer 100 b. The second rolling element 950 is disposed between the shaft portion 700 and the third ring structure 800. The first annular protrusion 520 includes a first step 521 and a second step 522 sequentially disposed on the inner surface 510 of the first annular structure 500, and an outer diameter r3 of the second step 522 is smaller than an outer diameter r2 of the first step 521, so as to form a space 710 in the shaft 700 for accommodating the second rolling element 950. The first holder 100a and the second holder 100b may be the same as the holder 100, and regarding the elements in the first holder 100a and the second holder 100b, reference may be made to the elements having the same name in the holder 100. In the present embodiment, the first top edge of the flange portion of the first holder 100a has a first gap distance (not numbered) with the first ring structure 500, the second top edge of the flange portion of the first holder 100a has a second gap distance (not numbered) with the third ring structure 800, and the sum of the first gap distance and the second gap distance is 0.1mm to 0.4 mm. The first top edge of the flange portion of the second retainer 100b has a first clearance distance (not otherwise numbered) from the third ring structure 800, the second top edge of the flange portion of the second retainer 100b has a second clearance distance (not otherwise numbered) from the second ring structure 600, and the sum of the first clearance distance and the second clearance distance is 0.1mm to 0.4 mm. The retainer is not provided with the flange part, so that the retainer needs to be configured with larger thickness to avoid serious oil leakage caused by overlarge annular structure clearance between the retainer and the bearing.

Oil retention test: a first test bearing was assembled, which was structurally comparable to bearing 2000, but first retainer 100a was replaced with a comparable retainer without a flange portion (i.e., heights H1 and H2 in fig. 3 were both 0). Equal weight lubricating fluid (weight W0 in this case) was injected into each of the first and third annular structures and each of the third and second annular structures of the first test bearing, the first test bearing was operated at 10rpm for 1 hour, the weight (W1) of the remaining lubricating fluid in each of the first and third annular structures and each of the third and second annular structures of the first test bearing was measured, and the leaked lubricating fluid weight (Δ W) (-W0-W1) was calculated. The test results are shown in table one, and it can be seen that the retainer of the present invention is effective in reducing the weight of the leaked lubricant.

And (3) torsion testing: the second test bearing and the comparison test bearing are assembled in a structure similar to that of the bearing 2000, but the comparison retainer in the comparison test bearing has no flange part and only includes the first hole, and the torsion values of the second test bearing and the comparison test bearing are respectively measured by using a torsion meter (brand name: IMADA; model number: FB-20K) to obtain 4kgf and 4 kgf.

Compared with the prior art, the retainer provided by the invention has the advantages that the flange part is arranged, so that the lubricating liquid in the bearing can be effectively prevented from leaking outwards, the lubricating effect of the bearing is further favorably maintained, and the service life of the bearing is prolonged. Rely on the oil storage tank to communicate with two adjacent holes, be favorable to the homogeneity that lubricated liquid distributes.

Furthermore, the retainer of the present invention may include both the first hole and the second hole, which is advantageous to avoid the contact friction between the retainer and other parts of the bearing, such as the first annular structure and the second annular structure, and the manufacturability of the retainer may be improved by only having one scoop-shaped structure for each hole.

The foregoing description is intended to be illustrative rather than limiting, and it will be appreciated by those skilled in the art that many modifications, variations or equivalents may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A retainer for a bearing, the retainer having an annular configuration, comprising:

a body portion defining a central axis, the body portion comprising:

a first surface;

a second protrusion adjacent to the second surface, the second protrusion protruding outward relative to the second surface to have a second height difference;

each hole comprises a first opening and a second opening, the first opening is arranged on the first surface of the body part, the second opening is arranged on the second surface of the body part, a spoon-shaped structure is arranged on the first opening or the second opening of each hole, and the spoon-shaped structure is formed by two arc-shaped inner walls adjacent to the first opening or the second opening;

wherein the plurality of holes comprise:

a plurality of first holes, each of which is provided with the spoon-shaped structure at the first opening; and

a plurality of second holes, each of which is provided with the spoon-shaped structure at the second opening,

wherein, the plurality of first holes or the plurality of second holes are arranged at equal angles.

2. The holder of claim 1, wherein: the retainer is made of plastic.

3. A bearing, comprising:

a first ring structure;

a second annular structure;

a retainer according to claim 1 or 2, disposed between the first annular structure and the second annular structure, a first top edge of the first protrusion of the flange portion being adjacent to an inner surface of the first annular structure, a second top edge of the second protrusion of the flange portion being adjacent to an inner surface of the second annular structure; and

the rolling pieces are correspondingly arranged in the holes of the retainer.

4. The bearing of claim 3, wherein: the first top edge and the first annular structure have a first gap distance, the second top edge and the second annular structure have a second gap distance, and the sum of the first gap distance and the second gap distance is 0.1mm to 0.4 mm.

5. The bearing of claim 3, wherein: the first annular structure includes a first annular protrusion disposed on the inner surface of the first annular structure, the second annular structure includes a second annular protrusion disposed on the inner surface of the second annular structure, the first annular protrusion and the second annular protrusion are adjacent to form a shaft, each rolling element is a first rolling element, and the bearing further includes:

a third annular structure disposed between the first and second annular structures and surrounding the shaft portion; and

the first retainer is disposed between the first annular structure and the third annular structure and surrounds the shaft portion, and the second retainer is disposed between the third annular structure and the second annular structure and surrounds the shaft portion.