Deep groove ball bearing with improved structure

Abstract

The invention relates to the technical field of bearings, in particular to a deep groove ball bearing with an improved structure, which comprises an outer ring and an inner ring, a cage type retainer is adaptively mounted between the outer ring and the inner ring, the cage type retainer is provided with a plurality of special-shaped mounting holes, and rolling bodies are arranged in the special-shaped mounting holes and used for separating and guiding the rolling bodies to roll at correct positions in the bearing. The deep groove ball bearing comprises an annular ring body and special-shaped mounting holes, the special-shaped mounting holes are evenly formed in the middle of the circumferential face of the annular ring body, annular baffles are arranged on the two sides of a body of the annular ring body, the annular baffles are clamped in clamping grooves of an outer ring and an inner ring respectively, and dustproof covers are arranged in the clamping grooves and located on the outer sides of the annular baffles. The guide surface is lubricated when the rolling body rotates and is lubricated, and heat can be effectively dissipated; the annular baffle can keep lubricating oil on the inner side of the cage type retainer, leakage of the lubricating oil is prevented, it is guaranteed that the bearing is continuously lubricated in the running process, the lubricating effect of the deep groove ball bearing is improved, and the service life of the deep groove ball bearing is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of bearings, in particular to a deep groove ball bearing with an improved structure. Background Art

[0002] Deep groove ball bearings are a widely used type of bearings. They have a simple structure, are easy to use, can withstand radial and axial loads, and have a high speed capability. They are widely used in the automotive industry, electric motors, household appliances, office machinery and other fields.

[0003] Deep groove ball bearings are usually composed of an outer ring, an inner ring, rolling elements and a cage. The cage is an important component of the bearing. Its main function is to isolate the rolling elements at equal distances and prevent the rolling elements from contacting each other, while guiding the rolling elements and keeping them in the bearing. The traditional rivet-type cage is a guide-type cage that is radially bored from its outer diameter and uses a ring to guard the rolling elements. Due to the closed structure, the guide surface is difficult to lubricate, especially during lubrication, so wear and burning often occur, reducing the service life of the bearing. Especially in dusty, humid or other pollutant environments, in order to prevent pollutants from entering and prevent dust, particles and other pollutants from entering the bearing, it is necessary to install a dust cover on the outside of the deep groove ball bearing cage. The dust cover will limit the heat dissipation inside the bearing, and the closed structure of the rivet-type cage makes it impossible to effectively dissipate the heat generated by the rolling elements during high-speed rotation in the cage, resulting in an increase in the bearing temperature, which seriously affects the service life of the bearing.

[0004] Therefore, the present invention provides a deep groove ball bearing with an improved structure to solve the problems raised in the above background technology. Summary of the invention

[0005] The purpose of the present invention is to provide a deep groove ball bearing with an improved structure, so as to solve the problems that the existing deep groove ball bearings suffer from wear and burning due to insufficient lubrication, and the heat inside the bearings cannot be effectively dissipated, which shortens the life of the bearings.

[0006] In order to solve the above technical problems, the present invention provides a deep groove ball bearing with an improved structure, comprising an outer ring and an inner ring, a cage-type retaining frame adapted to be installed between the outer ring and the inner ring body, the cage-type retaining frame is provided with a plurality of special-shaped mounting holes, rolling bodies are arranged in the special-shaped mounting holes, which are used to separate and guide the rolling bodies to roll in the correct position in the bearing, the special-shaped mounting holes are evenly arranged in the middle of the circumferential surface of the annular ring body, annular baffles are arranged on both sides of the main body of the annular ring body, the annular baffles are respectively clamped in the clamping grooves of the outer ring and the inner ring, and a dust cover is arranged in the clamping groove on the outside of the annular baffle.

[0007] A further improvement of the technical solution of the present invention is that the cage-type retaining frame includes a first frame body and a second frame body, the first frame body is composed of an annular baffle and a first annular ring body arranged on the annular baffle, the second frame body is composed of an annular baffle and a second annular ring body arranged on the annular baffle, and the first annular ring body and the second annular ring body are adapted to be spliced ​​into an annular ring body and a special-shaped mounting hole on the annular ring body.

[0008] A further improvement of the technical solution of the present invention is that: the first annular ring body is provided with wavy upper end faces A on both sides of the special-shaped mounting hole, and the second annular ring body is provided with wavy upper end faces B on both sides of the special-shaped mounting hole, and the upper end faces A are adapted to fit the upper end faces B.

[0009] A further improvement of the technical solution of the present invention is that: a heat dissipation hole is set on the outer side of the annular baffle, the heat dissipation hole extends to the wavy upper end surface A, the heat dissipation hole extends to the wavy upper end surface B, and rivets are set in the heat dissipation holes for fixing the first annular ring body and the second annular ring body when they are assembled.

[0010] A further improvement of the technical solution of the present invention is that the special-shaped mounting hole includes two arc surfaces opposite to each other in the axial direction of the annular ring body, grooves are respectively arranged at both ends of the two arc surfaces, and a limiter is arranged between the grooves, which is used to limit the two top surfaces of the rolling body along the width direction of the annular ring body.

[0011] A further improvement of the technical solution of the present invention is that the limit member is disc-shaped, the upper surface of the disc is a concave arc surface, the arc surface adapts to the two top surfaces of the rolling body along the width direction of the annular ring body; the outer arc surface of the rolling body along the axial direction of the annular ring body adapts to the two arc surfaces.

[0012] A further improvement of the technical solution of the present invention is that the card slot includes a card slot A and a card slot B, the card slot A is arranged at the edges on both sides of the inner arc surface of the outer ring body, and the card slot B is arranged at the edges on both sides of the outer arc surface of the inner ring body; the card slot A and the card slot B are respectively clamped at the upper and lower edges of the annular baffle.

[0013] A further improvement of the technical solution of the present invention is that: a groove A is provided on the inner arc surface of the outer ring, a groove B is provided on the outer arc surface of the inner ring, and the groove A and the groove B are adapted to install the rolling body together, and the rolling body can roll smoothly between the inner ring and the outer ring.

[0014] A further improvement of the technical solution of the present invention is that a first fillet is set between groove A and the inner arc surface of the outer ring, and the angle of the first fillet is 110 degrees to 150 degrees; a first fillet is set between groove B and the outer arc surface of the inner ring, and the angle of the first fillet is 110 degrees to 150 degrees.

[0015] A further improvement of the technical solution of the present invention is that a second fillet is provided at the edges on both sides of the inner arc surface of the inner ring, and the radius of the fillet is 1.7-1.9, which is convenient for installation with external equipment.

[0016] By adopting the above technical solution, the present invention has the following beneficial effects: 1. The deep groove ball bearing with improved structure provided by the present invention comprises an outer ring and an inner ring, the inner ring and the outer ring jointly provide a stable motion track for the rolling body, a cage-type retainer is adapted to be installed between the outer ring and the inner ring body, the cage-type retainer ensures that the rolling body is evenly distributed and moves correctly on the grooves of the inner ring and the outer ring, and the cage-type retainer is provided with special-shaped mounting holes so that when the rolling body rotates in the special-shaped mounting holes, the guide surface is lubricated during lubrication, and heat can be effectively dissipated in the cage-type retainer; the provision of the annular baffle can retain the lubricating oil on the inner side of the cage-type retainer to prevent its leakage, thereby ensuring that the bearing is continuously lubricated during operation, thereby improving the lubrication effect of the deep groove ball bearing and the service life of the deep groove ball bearing.

[0017] 2. The deep groove ball bearing with improved structure provided by the present invention comprises a cage-type retaining frame which is assembled by a first frame body and a second frame body, so as to facilitate the installation of rolling elements. The first annular ring body is provided with a wavy upper end face A, and the second annular ring body is provided with a wavy upper end face B. The upper end face A is adapted to fit the upper end face B. The wavy fitting surface prevents the first annular ring body and the second annular ring from being misaligned when being spliced ​​together, thereby improving the installation accuracy of the splicing of the first annular ring body and the second annular ring and improving the service life of the deep groove ball bearing.

[0018] 3. The deep groove ball bearing with an improved structure provided by the present invention has a heat dissipation hole on the outer side of the annular baffle of the deep groove ball bearing, the heat dissipation hole extends to the wavy upper end surface A, and the heat dissipation hole extends to the wavy upper end surface B. The design of the heat dissipation hole increases the heat dissipation surface of the cage retainer, which can disperse the heat generated by the rolling body rotating in the special-shaped mounting hole, improve the operating efficiency of the bearing, prevent the bearing damage caused by excessive temperature, and thus increase the service life of the bearing.

[0019] 4. The deep groove ball bearing with improved structure provided by the present invention realizes the limitation of the outer circumference of the rolling body in four directions through the two arc surfaces and the limit pieces in the special-shaped mounting hole, guides and drives the rolling body to roll on the groove, reduces the covering of the outer circumference of the rolling body by the cage retainer, increases the heat dissipation area of ​​the rolling body during rotation, reduces the temperature rise of the bearing, and increases the service life of the bearing. Grooves are respectively arranged at both ends of the two arc surfaces. The space in the grooves can perform a certain heat dissipation function for the heat generated when the rolling body rotates. Some viscous lubricating grease can be stored in the grooves. The lubricating grease is taken away when the rolling body rotates, and the rolling body is lubricated, thereby improving the lubrication effect of the rolling body.

[0020] 5. The deep groove ball bearing with improved structure provided by the present invention has a groove A set on the inner arc surface of the outer ring, and a groove B set on the outer arc surface of the inner ring. The groove A and the groove B are jointly adapted to install the rolling body, providing a rolling path for the rolling body, so that the rolling body can roll smoothly between the inner ring and the outer ring; a fillet is set between the groove A and the inner arc surface of the outer ring, and the angle of the fillet is 110 degrees to 150 degrees; a fillet is set between the groove B and the outer arc surface of the inner ring, and the angle of the fillet is 110 degrees to 150 degrees. The setting of the fillet can serve as a guide when installing the rolling body, so that the rolling body is easier to install into the groove during installation, reducing the resistance and damage risk during the assembly process, and improving the service life of the bearing.

[0021] 6. The deep groove ball bearing with improved structure provided by the present invention has fillets on the edges on both sides of the inner arc surface of the inner ring, and the radius of the fillets is 1.7~1.9, which facilitates the assembly of the deep groove ball bearing with external equipment, reduces the resistance and damage risk during the assembly process, and improves the service life of the bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 An exploded schematic diagram of a deep groove ball bearing with an improved structure; Figure 2 It is a schematic diagram of the cage retainer structure; Figure 3 A schematic diagram of the structure of the first frame and the second frame; Figure 4 is a schematic diagram of the first frame structure; Figure 5 It is the overall schematic diagram of the cage retainer; Figure 6 It is a schematic diagram of the structure of the special-shaped mounting hole; Figure 7 It is a cross-sectional view of the outer ring, inner ring and cage; Figure 8 for Figure 7 The enlarged schematic diagram of part A in the middle; Fig. 9 for Figure 7 A magnified schematic diagram of part B; Figure numerals: 1. outer ring; 2. inner ring; 3. dust cover; 4. cage retainer; 5. rolling element; 6. slot; 11. groove A; 12. first fillet; 13. second fillet; 21. groove B; 41. first frame; 42. second frame; 43. heat dissipation hole; 44. special-shaped mounting hole; 45. annular baffle; 46. annular ring body; 47. limiter; 48. groove; 49. arc surface; 61. slot A; 62. slot B; 411. first annular ring body; 412. upper end face A; 421. second annular ring body; 422. upper end face B. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The present invention is further explained below in conjunction with specific implementation modes.

[0028] like Figure 1-9As shown, the deep groove ball bearing with improved structure provided in this embodiment includes an outer ring 1 and an inner ring 2. A groove A11 is set on the inner arc surface of the outer ring 1, and a groove B21 is set on the outer arc surface of the inner ring 2. The groove A11 and the groove B21 are jointly adapted to install the rolling body 5, and the rolling body 5 can roll smoothly between the inner ring 2 and the outer ring 1. A cage retainer 4 is adapted to be installed between the outer ring 1 and the inner ring 2. The cage retainer 4 is provided with a plurality of special-shaped mounting holes 44. Rolling bodies 5 are arranged in the special-shaped mounting holes 44 for separating and guiding the rolling bodies 5 to roll in the correct position in the bearing. The special-shaped mounting holes 44 are evenly arranged in the middle of the circumferential surface of the annular ring body 46. Annular baffles 45 are arranged on both sides of the main body of the annular ring body 46. The annular baffles 45 are respectively clamped in the clamping grooves 6 of the outer ring 1 and the inner ring 2. A dust cover 3 is arranged in the clamping groove 6 on the outside of the annular baffle 45. The clamping groove 6 includes a clamping groove A61 and a clamping groove B62. The clamping groove A61 is arranged at the edges of both sides of the inner arc surface of the outer ring 1 body, and the clamping groove B62 is arranged at the edges of both sides of the outer arc surface of the inner ring 2 body; the clamping grooves A61 and B62 are respectively clamped at the upper and lower edges of the annular baffle 45, and the outer edges of the annular baffle 45 in the clamping grooves A61 and B62 A dust cover 3 is arranged on the side, which can effectively prevent dust, sand, moisture and other pollutants from entering the bearing, protect the inside of the bearing from being clean, reduce wear and corrosion caused by pollution, and thus extend the service life of the bearing. The inner ring and the outer ring jointly provide a stable motion track for the rolling element. A cage-type retainer is adapted to be installed between the outer ring and the inner ring body. The cage-type retainer ensures that the rolling element is evenly distributed and moves correctly on the grooves of the inner ring and the outer ring. The cage-type retainer has special-shaped mounting holes set therein, so that when the rolling element rotates in the special-shaped mounting holes, the lubricating oil in the bearing is lubricated on the guide surface during lubrication, and the heat can be effectively dissipated in the cage-type retainer; the setting of the annular baffle can retain the lubricating oil on the inside of the cage-type retainer to prevent it from leaking, thereby ensuring that the bearing is continuously lubricated during operation, and improving the lubrication effect of the deep groove ball bearing and the service life of the deep groove ball bearing.

[0029] like Figure 1~Figure 4As shown, in this embodiment, the cage retainer 4 includes a first frame body 41 and a second frame body 42, the first frame body 41 is composed of an annular baffle 45 and a first annular ring body 411 provided on the annular baffle 45, the second frame body 42 is composed of an annular baffle 45 and a second annular ring body 421 provided on the annular baffle 45, the first annular ring body 411 and the second annular ring body 421 are adapted to be spliced ​​into an annular ring body 46 and a special-shaped mounting hole 44 on the annular ring body 46. The first annular ring body 411 is provided with a wavy upper end face A412 on both sides of the special-shaped mounting hole 44, the second annular ring body 421 is provided with a wavy upper end face B422 on both sides of the special-shaped mounting hole 44, and the upper end face A412 is adapted to fit the upper end face B422. The cage retainer is assembled by setting a first frame body and a second frame body, which is convenient for installing the rolling body. The first annular ring body is provided with a wavy upper end face A, and the second annular ring body is provided with a wavy upper end face B. The upper end face A is adapted to fit the upper end face B. The wavy fitting surface prevents the first annular ring body and the second annular ring from being misaligned when spliced ​​together, thereby improving the installation accuracy of the splicing of the first annular ring body and the second annular ring and improving the service life of the deep groove ball bearing.

[0030] The special-shaped mounting hole 44 includes two arc surfaces 49 arranged opposite to each other in the axial direction of the annular ring body 46, grooves 48 are arranged at both ends of the two arc surfaces 49, and a stopper 47 is arranged between the grooves 48. The stopper 47 is used to limit the two top surfaces of the rolling body 5 along the width direction of the annular ring body 46. The stopper 47 is in the shape of a disk, and the upper surface of the disk is a concave arc surface, and the arc surface is adapted to the two top surfaces of the rolling body 5 along the width direction of the annular ring body 46; the outer arc surface of the rolling body 5 along the axial direction of the annular ring body 46 is adapted to the two arc surfaces 49. The deep groove ball bearing limits the outer circumference of the rolling body in four directions through the two arc surfaces and the limit pieces in the special-shaped mounting hole, guides and drives the rolling body to roll on the groove, reduces the coverage of the outer circumference of the rolling body by the cage retainer, increases the heat dissipation area of ​​the rolling body during rotation, reduces the temperature increase of the bearing, and increases the service life of the bearing. Grooves are respectively arranged at both ends of the two arc surfaces. The space in the grooves can perform a certain heat dissipation function for the heat generated when the rolling body rotates. Part of the viscous lubricating grease can be stored in the grooves, and the lubricating grease is taken away when the rolling body rotates, so as to lubricate the rolling body and improve the lubrication effect of the rolling body.

[0031] like Figure 1 , Figure 2 , Figure 3 , Figure 5 As shown, in this embodiment, a heat dissipation hole 43 is provided on the outer side of the annular baffle 45, the heat dissipation hole 43 extends to the wavy upper end surface A412, the heat dissipation hole 43 extends to the wavy upper end surface B422, and a rivet is provided in the heat dissipation hole 43 for fixing the first annular ring body 411 and the second annular ring body 421 when they are assembled.

[0032] like Figure 8 , Fig. 9 As shown, in this embodiment, a first fillet 12 is set between the groove A11 and the inner arc surface of the outer ring 1, and the angle of the first fillet 12 is 110 degrees to 150 degrees. A first fillet 12 is set between the groove B21 and the outer arc surface of the inner ring 2, and the angle of the first fillet 12 is 110 degrees to 150 degrees. The edges on both sides of the inner arc surface of the inner ring 2 are provided with second fillets 13, and the radius of the fillet 14 is 1.7 to 1.9, which is convenient for installation with external equipment; the deep groove ball bearing has a fillet set between the through groove A and the inner arc surface of the outer ring, and the angle of the fillet is 110 degrees to 150 degrees. A fillet is set between the groove B and the outer arc surface of the inner ring, and the angle of the fillet is 110 degrees to 150 degrees. The setting of the fillet can be used as a guide when installing the rolling body, so that the rolling body is easier to install in the groove during installation, reducing the resistance and damage risk during assembly, and improving the service life of the bearing. Fillets are set on the edges of both sides of the inner arc surface of the inner ring, and the radius of the fillets is 1.7~1.9, which facilitates the assembly of the deep groove ball bearing and external equipment, reduces the resistance and damage risk during the assembly process, and improves the service life of the bearing.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A deep groove ball bearing with improved structure, characterized in that: The invention comprises an outer ring (1) and an inner ring (2), wherein a cage retainer (4) is adapted to be installed between the outer ring (1) and the inner ring (2), wherein the cage retainer (4) is provided with a plurality of special-shaped mounting holes (44), wherein rolling bodies (5) are arranged in the special-shaped mounting holes (44) for separating and guiding the rolling bodies (5) to roll at the correct position in the bearing, wherein the special-shaped mounting holes (44) are evenly arranged in the middle of the circumferential surface of the annular ring body (46), and annular baffles (45) are arranged on both sides of the main body of the annular ring body (46), wherein the annular baffles (45) are respectively clamped in the clamping grooves (6) of the outer ring (1) and the inner ring (2), and a dust cover (3) is arranged in the clamping groove (6) on the outside of the annular baffle (45).

2. The deep groove ball bearing with improved structure according to claim 1, characterized in that: The cage retainer (4) comprises a first frame body (41) and a second frame body (42), wherein the first frame body (41) is composed of an annular baffle (45) and a first annular ring body (411) disposed on the annular baffle (45), and the second frame body (42) is composed of an annular baffle (45) and a second annular ring body (421) disposed on the annular baffle (45), wherein the first annular ring body (411) and the second annular ring body (421) are adapted to be spliced ​​to form an annular ring body (46) and a special-shaped mounting hole (44) on the annular ring body (46).

3. The deep groove ball bearing with improved structure according to claim 2, characterized in that: The first annular ring body (411) is provided with wavy upper end surfaces A (412) on both sides of the special-shaped mounting hole (44), and the second annular ring body (421) is provided with wavy upper end surfaces B (422) on both sides of the special-shaped mounting hole (44), and the upper end surfaces A (412) are adapted to fit the upper end surfaces B (422).

4. The deep groove ball bearing with improved structure according to claim 3 is characterized in that: A heat dissipation hole (43) is provided on the outer side surface of the annular baffle (45), the heat dissipation hole (43) extends to the wavy upper end surface A (412), the heat dissipation hole (43) extends to the wavy upper end surface B (422), and a rivet is provided in the heat dissipation hole (43) for fixing the first annular ring body (411) and the second annular ring body (421) when they are assembled.

5. The deep groove ball bearing with improved structure according to claim 4, characterized in that: The special-shaped mounting hole (44) comprises two arc surfaces (49) arranged opposite to each other in the axial direction of the annular ring body (46), grooves (48) are respectively arranged at both ends of the two arc surfaces (49), and a limiting member (47) is arranged between the grooves (48). The limiting member (47) is used to limit the two top surfaces of the rolling body (5) along the width direction of the annular ring body (46).

6. The deep groove ball bearing with improved structure according to claim 5, characterized in that: The limiting member (47) is in the shape of a disk, the upper surface of which is a concave arc surface, the arc surface being adapted to the two top surfaces of the rolling body (5) along the width direction of the annular ring body (46); the outer arc surface of the rolling body (5) along the axial direction of the annular ring body (46) being adapted to the two arc surfaces (49).

7. The deep groove ball bearing with improved structure according to claim 6, characterized in that: The card slot (6) comprises a card slot A (61) and a card slot B (62), wherein the card slot A (61) is arranged at The outer ring (1) body has edges on both sides of the inner arc surface, and the clamping grooves B (62) are arranged on the edges on both sides of the outer arc surface of the inner ring (2) body; the clamping grooves A (61) and the clamping grooves B (62) are respectively clamped on the upper and lower edges of the annular baffle (45).

8. The deep groove ball bearing with improved structure according to claim 7, characterized in that: A groove A (11) is provided on the inner arc surface of the outer ring (1), and a groove B (21) is provided on the outer arc surface of the inner ring (2). The groove A (11) and the groove B (21) are adapted to mount the rolling body (5) together, and the rolling body (5) can roll smoothly between the inner ring (2) and the outer ring (1).

9. The deep groove ball bearing with improved structure according to claim 8, characterized in that: A first fillet (12) is provided between the groove A (11) and the inner arc surface of the outer ring (1), and the angle of the first fillet (12) is 110 degrees to 150 degrees. A first fillet (12) is provided between the groove B (21) and the outer arc surface of the inner ring (2), and the angle of the first fillet (12) is 110 degrees to 150 degrees.

10. The deep groove ball bearing with improved structure according to claim 9, characterized in that: Second rounded corners (13) are provided at the edges of both sides of the inner arc surface of the inner ring (2), and the radius of the rounded corners (14) is 1.7 to 1.9, so as to facilitate installation with external equipment.

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