A microwave resonant cavity for vapor deposition

Abstract

The present application relates to a microwave resonant cavity for vapor deposition, which includes a resonant cavity shell, a waveguide structure and a tuning element. A resonant cavity is formed in the resonant cavity shell, and a waveguide feed port connected to the resonant cavity is also provided at the bottom of the resonant cavity shell; the waveguide structure has a first channel, the waveguide structure is installed on the resonant cavity shell, and one end of the first channel is connected to the waveguide feed port; a tuning element is movably provided on the waveguide structure, and one end of the tuning element extends into the first channel. The microwave resonant cavity provided in the present application is provided with a tuning element on the waveguide structure. On the basis of adjusting the reflection coefficient by a traditional microwave tuner, the linear reflection coefficient can be adjusted secondarily by adjusting the length of the tuning element extending into the first channel, which effectively improves the feeding power of the microwave resonant cavity, thereby reducing the loss of microwave energy, which is conducive to the stable operation of the microwave source and improves the deposition quality.

Description

Technical Field

[0001] The present application relates to the technical field of optical fiber preform processing equipment, and in particular to a microwave resonant cavity for vapor deposition. Background Art

[0002] Plasma chemical vapor deposition (PCVD) is one of the main processes for optical fiber preform processing. This process has the characteristics of precise and meticulous control of the deposition process, and the microwave resonant cavity is the core part of the processing equipment. Under low pressure, due to the action of high-frequency microwaves, the raw gas entering the quartz reaction tube is partially ionized into an activated plasma state. These active ions can react quickly, and the reaction products are deposited on the inner surface of the tube wall in a glassy state. Because its microwave resonant cavity can move quickly and the deposition thickness of a single layer is thin, it is easy to manufacture fine and complex refractive index profiles.

[0003] At present, the existing microwave resonant cavities used for plasma chemical vapor deposition are mainly of two types: coaxial and cylindrical. The coaxial type is connected to the resonant cavity through a single coaxial line and is suitable for processing quartz reaction tubes with relatively small outer diameters. The cylindrical type is connected to the resonant cavity through a single rectangular waveguide and is suitable for processing quartz reaction tubes with relatively large outer diameters.

[0004] The coaxial type is not suitable for manufacturing large-diameter optical fiber preforms due to structural limitations. In addition, when high-power microwaves are input, the cavity and coaxial waveguide are prone to heat up, which may cause the microwave cavity or coaxial line to burn out in severe cases.

[0005] The cylindrical structure is simple, easy to process and manufacture, and has excellent deposition performance. As the tube wall thickness gradually increases, the inner diameter of the reaction tube continues to decrease, the plasma density and morphology change, resulting in changes in the load of the microwave cavity. Therefore, there is a situation where the microwave and plasma loads cannot match, causing most of the microwave energy to be reflected to the microwave source end, resulting in microwave energy loss and unstable microwave source operation.

[0006] Since the plasma distribution of a single coaxial line or a single rectangular waveguide is relatively concentrated, when high-power microwaves are input, there is a risk that the reaction liner will be deflated during the process, causing the process to be unable to continue and resulting in a waste of raw materials. Summary of the invention

[0007] The embodiment of the present application provides a microwave resonant cavity for vapor deposition to solve the problem in the related art that microwaves and plasma loads cannot be matched, so that most of the microwave energy is reflected to the microwave source end, resulting in microwave energy loss and unstable operation of the microwave source.

[0008] The present application provides a microwave resonant cavity for vapor deposition, which includes:

[0009] A resonant cavity shell, wherein a resonant cavity is formed in the resonant cavity shell, and a waveguide feed port communicating with the resonant cavity is also provided at the bottom of the resonant cavity shell;

[0010] A waveguide structure, wherein the waveguide structure has a first channel, the waveguide structure is mounted on the resonant cavity housing, and one end of the first channel is connected to the waveguide feed port;

[0011] Furthermore, a tuning component is movably provided on the waveguide structure, and one end of the tuning component extends into the first channel.

[0012] In some embodiments, there are multiple waveguide feed ports, which are arranged at intervals along the axial direction of the resonant cavity shell, multiple first channels are formed in the waveguide structure, and each of the waveguide feed ports is connected to a first channel of the waveguide structure.

[0013] In some embodiments, the microwave resonant cavity further includes a power divider, which is provided with a microwave input port and a plurality of microwave output ports. The power divider is mounted on the waveguide structure, and each of the microwave output ports is connected to one of the first channels.

[0014] In some embodiments, there are two waveguide feed ports, two first channels, and two microwave output ports, so that the power divider divides the microwave power into two.

[0015] In some embodiments, the cross-section of the waveguide feed is rectangular, and the length of the long side of the waveguide feed is twice the length of the short side.

[0016] In some embodiments, the cross-section of the waveguide feed is rectangular, and the center distance a between two adjacent waveguide feeds is configured to be 1 / 2λ≤a≤λ, where λ is the wavelength of microwaves in a vacuum.

[0017] In some embodiments, a second channel for the quartz reaction tube to pass through is opened at the end of the resonant cavity shell, and the second channel is coaxial with and connected to the resonant cavity;

[0018] A first cooling channel is also provided in the resonant cavity shell, and the first cooling channel surrounds the outside of the second channel;

[0019] The waveguide structure is provided with two second cooling channels connected with the first cooling channel, and the waveguide structure is provided with a coolant inlet and a coolant outlet, and the coolant inlet and the coolant outlet are respectively connected with the two second cooling channels.

[0020] In some embodiments, a second channel for the quartz reaction tube to pass through is opened at the end of the resonant cavity shell, and the second channel is coaxial with and connected to the resonant cavity;

[0021] An inner diameter variable ring is connected to the end of the resonance cavity shell, and the inner diameter variable ring is coaxial with and communicated with the second channel.

[0022] In some embodiments, the variable inner diameter ring comprises:

[0023] An outer ring, wherein a circular arc-shaped mounting portion is formed on one wall surface of the outer ring;

[0024] An inner ring, the inner ring being movably arranged in the mounting portion, and a plurality of guide grooves extending in the radial direction are arranged on a wall surface of the inner ring facing the outer ring;

[0025] A plurality of arc-shaped blades, wherein the blades are located between the outer ring and the inner ring, one wall surface of the blade is rotatably connected to the outer ring, and the other wall surface is provided with a guide rod moving in the guide groove;

[0026] Furthermore, the inner ring is provided with an operating portion for driving the inner ring to rotate around its own axis on the mounting portion.

[0027] In some embodiments, a mounting hole is provided on the outer ring, a rotating shaft is provided on the wall surface of the blade, and the rotating shaft is located in the mounting hole;

[0028] And / or, a clamping groove is provided on the inner wall of the mounting portion, a clamping member is installed in the clamping groove, and the clamping member abuts against the wall surface of the inner ring away from the outer ring.

[0029] The beneficial effects of the technical solution provided by this application include:

[0030] The embodiment of the present application provides a microwave resonant cavity for vapor deposition. The microwave resonant cavity is provided with a tuning element on the waveguide structure. On the basis of adjusting the reflection coefficient by a traditional microwave tuner, the linear reflection coefficient can be adjusted secondarily by adjusting the length of the tuning element extending into the first channel, thereby effectively improving the feed power of the microwave resonant cavity, thereby reducing the loss of microwave energy, facilitating the stable operation of the microwave source, and improving the deposition quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 A schematic diagram of a resonant cavity shell provided in an embodiment of the present application;

[0033] Figure 2A schematic diagram of a microwave resonant cavity for vapor deposition provided in an embodiment of the present application;

[0034] Figure 3 A cross-sectional view of a microwave resonant cavity for vapor deposition provided in an embodiment of the present application;

[0035] Figure 4 A comparison diagram of linear reflection coefficient curves provided in the embodiments of the present application;

[0036] Figure 5 A cross-sectional view of a resonant cavity housing and a waveguide structure provided in an embodiment of the present application;

[0037] Figure 6 A schematic diagram of a microwave resonant cavity for vapor deposition provided in an embodiment of the present application (with a variable inner diameter ring installed);

[0038] Figure 7 A schematic diagram of a variable inner diameter ring provided in an embodiment of the present application;

[0039] Figure 8 A schematic diagram of an outer ring provided in an embodiment of the present application;

[0040] Fig. 9 A schematic diagram of an inner ring provided in an embodiment of the present application;

[0041] Fig.10 A schematic diagram of a blade provided in an embodiment of the present application.

[0042] In the figure: 1. resonant cavity shell; 2. resonant cavity body; 3. waveguide feed; 4. waveguide structure; 5. first channel; 6. tuning element; 7. power divider; 8. microwave input port; 9. microwave output port; 10. second channel; 11. first cooling channel; 12. second cooling channel; 13. coolant inlet; 14. coolant outlet; 15. inner diameter variable ring; 16. outer ring; 17. mounting portion; 18. inner ring; 19. guide groove; 20. blade; 21. guide rod; 22. operating portion; 23. mounting hole; 24. rotating shaft; 25. slot; 26. clamping member. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0044] See also Figure 1 , Figure 2 and Figure 3 As shown, an embodiment of the present application provides a microwave resonant cavity for vapor deposition, which includes a resonant cavity shell 1, a waveguide structure 4 and a tuning component 6. A resonant cavity 2 is formed in the resonant cavity shell 1, and the resonant cavity 2 is cylindrical to facilitate the placement of a quartz reaction tube. A waveguide feed 3 connected to the resonant cavity 2 is also provided at the bottom of the resonant cavity shell 1. The waveguide structure 4 has a first channel 5, and the cross-sectional size of the first channel 5 is the same as the cross-sectional size of the waveguide feed 3. The waveguide structure 4 is installed on the resonant cavity shell 1, and one end of the first channel 5 is connected to the waveguide feed 3; a tuning component 6 is movably provided on the waveguide structure 4, and one end of the tuning component 6 extends into the first channel 5.

[0045] The microwave resonant cavity provided in the embodiment of the present application is provided with a tuning element 6 on the waveguide structure 4. On the basis of adjusting the reflection coefficient by a traditional microwave tuner, the linear reflection coefficient can be adjusted secondarily by adjusting the length of the tuning element 6 extending into the first channel 5, thereby effectively improving the feeding power of the microwave resonant cavity, thereby reducing the loss of microwave energy, facilitating the stable operation of the microwave source, and improving the deposition quality.

[0046] There are two methods for adjusting the linear reflection coefficient using the tuning element 6 provided in the embodiment of the present application. The first method is to separate the resonant cavity shell 1 from the waveguide structure 4, connect the microwave test water load to the waveguide structure 4, turn on the microwave, and adjust the tuning element 6 on the waveguide structure 4 when the tuner is not working, so that the linear reflection coefficient is below 0.1, or even close to 0; the second method is to directly place the quartz reaction tube in the middle of the resonant cavity shell 1, pass a certain flow of high-purity gas, turn on the microwave, and adjust the tuning element 6 on the waveguide structure 4 when the tuner is not working, so that the linear reflection coefficient is below 0.1, or even close to 0.

[0047] There are many options for the tuning element 6. For example, as an example, a screw can be used. For example, as another example, a screw rod can be used. A threaded hole is provided on the waveguide structure 4, and a screw or a screw rod is screwed into the threaded hole.

[0048] Since the plasma distribution of a single coaxial line or a single rectangular waveguide is relatively concentrated, when high-power microwaves are input, the reaction liner may collapse during the process, causing the process to be unable to proceed and resulting in a waste of raw materials. In order to solve this problem, in some preferred embodiments, see Figure 1 and Figure 3As shown, there are multiple waveguide feed ports 3, which are arranged at intervals along the axial direction of the resonant cavity shell 1, and multiple first channels 5 are formed in the waveguide structure 4. Each first channel 5 is configured with at least one tuning element 6. The number of first channels 5 is the same as the number of waveguide feed ports 3, and they are distributed one by one, and each waveguide feed port 3 is connected to a first channel 5 of the waveguide structure 4.

[0049] By arranging a plurality of first channels 5 in the waveguide structure 4 and arranging a plurality of waveguide feed ports 3 on the resonant cavity shell 1, so that the first channels 5 are connected to the waveguide feed ports 3 in a one-to-one correspondence, the microwave power can be divided into multiple parts, thereby dispersing the plasma in the resonant cavity 2 to avoid concentration, thereby reducing the risk of the quartz reaction tube being deflated.

[0050] In order to evenly distribute the microwave power, the sizes of the waveguide feed ports 3 are the same, and the sizes of the first channels 5 are the same.

[0051] In order to disperse the microwave power so that microwaves can enter each first channel 5, see Figure 2 and Figure 3 As shown, in some preferred embodiments, the microwave resonant cavity further includes a power divider 7, on which a microwave input port 8 and a plurality of microwave output ports 9 are provided, and the power divider 7 is installed on the waveguide structure 4 so that the waveguide structure 4 is located between the power divider 7 and the resonant cavity shell 1, and each of the microwave output ports 9 is connected to one of the first channels 5, and the microwave input port 8, the microwave output port 9, the first channel 5 are connected to the waveguide feed port 3 to introduce the microwave into the resonant cavity 2.

[0052] Preferably, see Figure 1 and Figure 3 As shown, the waveguide feed ports 3 are two, the first channels 5 are two, and the microwave output ports 9 are two, so that the power divider 7 divides the microwave power into two, a strong electric field coupling effect can be obtained in the resonant cavity 2, and the plasma distribution is more axially symmetrical. At this time, the waveguide structure 4 has two first channels 5, making the waveguide structure 4 a double waveguide structure, see Figure 4 As shown, the lower limit 0 represents perfect matching, and the upper limit 1 represents total reflection. Compared with the single waveguide structure with a first channel 5, the dual waveguide structure can adjust the linear reflection coefficient to be below 0.1 by using the tuning element 6, which is more conducive to improving the feeding power of the microwave resonant cavity.

[0053] There are many options for the shape of the waveguide feed port 3. Preferably, see Figure 1As shown, the cross section of the waveguide feed port 3 is rectangular, and the long side length of the waveguide feed port 3 is twice the short side length. When there are multiple waveguide feed ports 3, the long sides of each waveguide feed port 3 are parallel, and the short sides of each waveguide feed port 3 are also parallel.

[0054] Correspondingly, the end of each first channel 5 used to connect the waveguide feed port 3 and the microwave output port 9 is also rectangular, and the length of the long side of the end is twice the length of the short side.

[0055] See also Figure 1 As shown, the cross section of the waveguide feed 3 is rectangular, and the center distance a of two adjacent waveguide feeds 3 is configured to be 1 / 2λ≤a≤λ, where λ is the wavelength of microwaves in a vacuum. In this range, it is beneficial for the plasma to be evenly distributed.

[0056] In order to adapt to different temperature environments, the present application also designs a cooling channel in the microwave resonant cavity. Specifically, see Figure 3 and Figure 5 As shown, a second channel 10 for the quartz reaction tube to pass through is opened at the end of the resonant cavity shell 1, and the second channel 10 is coaxial with and connected to the resonant cavity body 2; a first cooling channel 11 is also provided in the resonant cavity shell 1, and the first cooling channel 11 is C-shaped and surrounds the outside of the second channel 10; two second cooling channels 12 connected to the first cooling channel 11 are provided on the waveguide structure 4, and a coolant inlet 13 and a coolant outlet 14 are provided on the waveguide structure 4, and the coolant inlet 13 and the coolant outlet 14 are respectively connected to the two second cooling channels 12.

[0057] In order to ensure the sealing effect, a rubber ring may be used to seal the joint between the first cooling channel 11 and the second cooling channel 12 .

[0058] See also Figure 3 As shown, the second channels 10 at both ends of the resonant cavity shell 1 can be provided with first cooling channels 11 , and each first cooling channel 11 corresponds to two second cooling channels 12 .

[0059] Since quartz reaction tubes have various sizes, current microwave resonant cavities can only be used for quartz reaction tubes of one size. If a quartz reaction tube of another size is used, a matching microwave resonant cavity needs to be reconfigured, which will inevitably increase production costs. In order to reduce costs, microwave resonant cavities can be used for quartz reaction tubes of different sizes. Figure 2 , Figure 3 , Figure 6 and Figure 7As shown, the end of the resonant cavity shell 1 is provided with a second channel 10 for the quartz reaction tube to pass through, and the second channel 10 is coaxial with and connected to the resonant cavity body 2; the end of the resonant cavity shell 1 is connected with an inner diameter variable ring 15, and the inner diameter variable ring 15 is coaxial with and connected to the second channel 10. By providing the inner diameter variable ring 15, when the size of the quartz reaction tube changes, the inner diameter of the inner diameter variable ring 15 is adjusted, so that the microwave resonant cavity of the present application can continue to be used.

[0060] See also Figure 7 , Figure 8 , Fig. 9 and Fig.10 As shown, the variable inner diameter ring 15 includes an outer ring 16, an inner ring 18 and a plurality of arc-shaped blades 20, a circular arc-shaped mounting portion 17 is formed on one wall surface of the outer ring 16, the inner ring 18 is movably arranged in the mounting portion 17, a plurality of radially extending guide grooves 19 are arranged on the wall surface of the inner ring 18 facing the outer ring 16, the blades 20 are located between the outer ring 16 and the inner ring 18, one wall surface of the blade 20 is rotatably connected to the outer ring 16, and a guide rod 21 moving in the guide groove 19 is arranged on the other wall surface, and the inner ring 18 is also provided with an operating portion 22 for driving the inner ring 18 to rotate around its own axis on the mounting portion 17.

[0061] All the blades 20 are arranged in sequence so that all the blades 20 jointly form a channel in the middle of the inner diameter variable ring 15, and the inner diameter of the channel can be changed during the rotation of the inner ring 18. Specifically, when the inner ring 18 is driven to rotate around its own axis by the operating part 22, one end of the blade 20 rotates on the outer ring 16, and the guide rod 21 at the other end moves in the guide groove 19 on the inner ring 18, thereby realizing the adjustment of the inner diameter.

[0062] See also Figure 8 and Fig.10 As shown, a mounting hole 23 is provided on the outer ring 16, and a rotating shaft 24 is provided on the wall surface of the blade 20. The aperture of the mounting hole 23 is slightly larger than the outer diameter of the rotating shaft 24. The rotating shaft 24 is located in the mounting hole 23, thereby achieving the purpose of the blade 20 rotating on the outer ring 16.

[0063] In order to ensure that the inner ring 18 and the outer ring 16 are installed firmly and prevent the inner ring 18 from being separated from the outer ring 16 during rotation, see Figure 7 and Figure 8 As shown, a clamping groove 25 is provided on the inner wall of the mounting portion 17 , and a clamping member 26 is installed in the clamping groove 25 . The clamping member 26 abuts against the wall surface of the inner ring 18 away from the outer ring 16 .

[0064] The clamping member 26 can be in the shape of a ring and fits in the ring-shaped clamping groove 25 .

[0065] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application 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 a limitation on the present application. 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 an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0066] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0067] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A microwave resonant cavity for vapor deposition, characterized in that: It includes: A resonant cavity shell (1), wherein a resonant cavity body (2) is formed in the resonant cavity shell (1), and a waveguide feed port (3) communicating with the resonant cavity body (2) is also provided at the bottom of the resonant cavity shell (1); A waveguide structure (4), the waveguide structure (4) having a first channel (5), the waveguide structure (4) being mounted on the resonant cavity housing (1), and one end of the first channel (5) being in communication with the waveguide feed port (3); Furthermore, a tuning element (6) is movably provided on the waveguide structure (4), and one end of the tuning element (6) extends into the first channel (5); There are two waveguide feed ports (3), which are spaced apart along the axial direction of the resonant cavity housing (1); two first channels (5) are formed in the waveguide structure (4), and each of the waveguide feed ports (3) is connected to a first channel (5) of the waveguide structure (4); The microwave resonant cavity further comprises a power divider (7), the power divider (7) being provided with a microwave input port (8) and two microwave output ports (9), the power divider (7) being mounted on the waveguide structure (4), and each of the microwave output ports (9) being connected to one of the first channels (5), and the two microwave output ports (9) enabling the power divider (7) to divide the microwave power into two; A second channel (10) for the quartz reaction tube to pass through is provided at the end of the resonant cavity shell (1), and the second channel (10) is coaxial with and communicates with the resonant cavity body (2); An inner diameter variable ring (15) is connected to the end of the resonant cavity shell (1), and the inner diameter variable ring (15) is coaxial with and communicates with the second channel (10); The inner diameter variable ring (15) comprises: An outer ring (16), wherein a circular arc-shaped mounting portion (17) is formed on a wall surface of the outer ring (16); an inner ring (18), the inner ring (18) being movably disposed in the mounting portion (17), and a plurality of guide grooves (19) extending in the radial direction being disposed on a wall surface of the inner ring (18) facing the outer ring (16); a plurality of arc-shaped blades (20), wherein the blades (20) are located between the outer ring (16) and the inner ring (18), one wall surface of the blade (20) is rotatably connected to the outer ring (16), and the other wall surface is provided with a guide rod (21) that moves in the guide groove (19); Furthermore, the inner ring (18) is provided with an operating portion (22) for driving the inner ring (18) to rotate around its own axis on the mounting portion (17).

2. The microwave resonant cavity for vapor deposition according to claim 1, characterized in that: The cross section of the waveguide feed port (3) is rectangular, and the length of the long side of the waveguide feed port (3) is twice the length of the short side.

3. The microwave resonant cavity for vapor deposition according to claim 1, characterized in that: The cross section of the waveguide feed port (3) is rectangular, and the center distance a between two adjacent waveguide feed ports (3) is configured to be 1 / 2λ≤a≤λ, where λ is the wavelength of microwaves in vacuum.

4. The microwave resonant cavity for vapor deposition according to claim 1, characterized in that: A second channel (10) for the quartz reaction tube to pass through is provided at the end of the resonant cavity shell (1), and the second channel (10) is coaxial with and communicates with the resonant cavity body (2); A first cooling channel (11) is also provided in the resonant cavity shell (1), and the first cooling channel (11) surrounds the outside of the second channel (10); The waveguide structure (4) is provided with two second cooling channels (12) connected to the first cooling channel (11), and the waveguide structure (4) is provided with a cooling liquid inlet (13) and a cooling liquid outlet (14), and the cooling liquid inlet (13) and the cooling liquid outlet (14) are respectively connected to the two second cooling channels (12).

5. The microwave resonant cavity for vapor deposition according to claim 1, characterized in that: The outer ring (16) is provided with a mounting hole (23), a rotating shaft (24) is provided on a wall surface of the blade (20), and the rotating shaft (24) is located in the mounting hole (23); And / or, a clamping groove (25) is provided on the inner wall of the mounting portion (17), a clamping member (26) is installed in the clamping groove (25), and the clamping member (26) abuts against the wall surface of the inner ring (18) away from the outer ring (16).

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