Bowl mill roller assembly

Abstract

The bowl type medium-speed coal mill tire type grinding roller device belongs to the technical field of coal mills and discloses a bowl type medium-speed coal mill tire type grinding roller device, which comprises a coal mill body, a driving structure is installed at the bottom end of the coal mill body, a grinding disc is arranged in the coal mill body, grinding rollers are arranged above the grinding disc, each grinding roller is provided with a cleaning assembly at the top end, each grinding roller is fixedly installed at the bottom end of a tripod, a lubricating assembly is arranged in the tripod, the bottom end of the cleaning head can be contacted with the grinding roller in the process of rotation of the grinding roller through the arrangement of the cleaning assembly, the surface of the grinding roller tire is cleaned through the cleaning head, the surface of the grinding roller tire is cleaned, the normal work of the grinding roller is not affected by the attachment of coal powder or other materials, the surface of the grinding roller tire is cleaned, the frictional resistance during the operation of the equipment is reduced, and the safety of the equipment is improved.

Description

Technical Field

[0001] This invention belongs to the field of coal mill technology, specifically a bowl-type medium-speed coal mill roller device. Background Technology

[0002] A bowl-type medium-speed coal mill is a device used for grinding and pulverizing coal. It typically consists of a bowl-shaped grinding disc, bowl-shaped grinding rollers, a conveying device, a motor, and a reducer. Inside the equipment, the coal is ground into fine powder by the action of the grinding disc and grinding rollers, and then output or further processed through the conveying device.

[0003] This equipment is mainly used in coal grinding systems to meet the requirements of coal powder particle size and quality in industries such as thermal power generation, metallurgy, and chemical industry. Bowl-type medium-speed coal mill has the characteristics of simple structure, stable operation, high coal grinding efficiency, and strong adaptability, and therefore it has been widely used in the field of coal grinding.

[0004] The wheel-type grinding roller device of a bowl-type medium-speed coal mill refers to the grinding roller on the grinding disc. Its structure is similar to a tire and is usually composed of grinding roller bearings, grinding roller tires, grinding roller seats, and other components. This design allows the grinding roller to rotate on the grinding disc and effectively grind and crush coal. During the operation of the equipment, some dirt may accumulate on the surface of the grinding roller tire due to the adhesion of coal powder or other materials. This dirt may affect the normal operation of the grinding roller, thereby increasing the frictional resistance during equipment operation and indirectly affecting the safety of the equipment. Summary of the Invention

[0005] The purpose of this invention is to provide a bowl-type medium-speed coal mill roller device to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a bowl-type medium-speed coal mill roller device, comprising a coal mill body, a drive structure installed at the bottom of the coal mill body, a grinding disc arranged inside the coal mill body, a grinding roller arranged above the grinding disc, multiple grinding rollers arranged, a cleaning component arranged at the top of each grinding roller, each grinding roller fixedly installed at the bottom of a tripod, a lubrication component arranged inside the tripod, and a hydraulic tie rod installed at the bottom of the tripod;

[0007] The cleaning assembly includes a cleaning head disposed at the top of the grinding roller. The cleaning heads are evenly distributed, and the top of each cleaning head is slidably mounted on the inner wall of a connecting tube. Each connecting tube is fixedly mounted on the bottom of a second connecting plate, which is slidably mounted on the inner wall of a tripod via a moving assembly.

[0008] As a further technical solution of the present invention, the bottom end of the cleaning head is inclined.

[0009] As a further technical solution of the present invention, the moving component includes a fixing block fixedly installed on the top of the second connecting plate. A protrusion is provided on one side of the fixing block, and a connecting rope is fixedly connected to one side of the protrusion. The end of the connecting rope away from the protrusion is installed on the outer wall of the second connecting shaft. A second gear is fixedly installed on the outer wall of the second connecting shaft. A first gear is meshed with one side of the second gear. A first connecting shaft is fixedly connected to the inner wall of the first gear. A second motor is fixedly connected to one end of the first connecting shaft. The second motor is installed inside the motor box, and the motor box is fixedly installed on the side wall of the tripod.

[0010] As a further technical solution of the present invention, a second spring is connected between the cleaning head and the connecting tube.

[0011] As a further technical solution of the present invention, the first gear is configured as a sector gear.

[0012] As a further technical solution of the present invention, the second connecting shaft is rotatably mounted on the inner wall of the tripod, and a first spring is installed between the second connecting shaft and the tripod.

[0013] As a further technical solution of the present invention, a third connecting rod is fixedly connected to one side of the fixing block, the third connecting rod is slidably installed on the inner wall of the tripod, and a third spring is provided on the outer wall of the third connecting rod.

[0014] As a further technical solution of the present invention, the lubrication assembly includes a first liquid outlet hole opened inside the tripod, a baffle slidably installed inside the first liquid outlet hole, a first connecting rod fixedly installed at the top of the baffle, a second connecting rod fixedly connected to the top of the first connecting rod, a first connecting plate fixedly installed at the top of the second connecting rod, a threaded rod embedded in the inner wall of the first connecting plate, a first motor fixedly installed at the top of the threaded rod, the first motor fixedly installed on one side of the fixed plate, and the fixed plate fixedly installed at the top of the tripod.

[0015] As a further technical solution of the present invention, a sealing gasket is fixedly installed at the bottom end of the baffle, the sealing gasket is embedded in the inner wall of the second liquid outlet hole, and the second liquid outlet hole is located at the bottom end of the first liquid outlet hole.

[0016] As a further technical solution of the present invention, a liquid filling hole is provided inside the top of the tripod, and a liquid filling plug is slidably installed inside the liquid filling hole.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. This invention, through the setting of the cleaning component, can contact the bottom end of the cleaning head during the rotation of the grinding roller, and clean the surface of the grinding roller tire through the cleaning head. This avoids the accumulation of dirt on the surface of the grinding roller tire due to the adhesion of coal powder or other materials. This dirt may affect the normal operation of the grinding roller, thereby increasing the frictional resistance during equipment operation and indirectly affecting the safety of the equipment. Cleaning the surface of the grinding roller tire not only helps to reduce the frictional resistance during equipment operation, but also helps to improve the safety of the equipment.

[0019] 2. By incorporating a movable component, this invention allows for the activation of a second motor via an external power source when cleaning the surface of the grinding roller tire is required. Since the input of the second motor is electrically connected to the external power source via a wire, and its output is fixedly connected to the first connecting shaft, the activation of the second motor drives the rotation of the first connecting shaft. This rotation drives the rotation of the first gear, which in turn drives the rotation of the second gear. The rotation of the second gear unwinds the connecting rope, causing the protrusion to move towards one side of the fixed block. Because the side of the protrusion closest to the fixed block is sloped, the protrusion contacts the fixed block, causing it to slide to one side. The movement of the fixed block moves the second connecting plate, which in turn moves the connecting tube. This movement of the connecting tube then moves the cleaning head, causing it to move at the top of the grinding roller for cleaning, further improving the cleaning effect.

[0020] 3. Through the arrangement of the lubrication components, when lubrication of the wheel-type grinding roller device of the bowl-type medium-speed coal mill is required, the threaded rod is first started by an external power source. The start of the threaded rod drives the first connecting plate to move, the movement of the first connecting plate drives the movement of the second connecting rod, the movement of the second connecting rod drives the movement of the first connecting rod, and the movement of the first connecting rod drives the movement of the baffle. This causes the bottom end of the baffle to separate from the top end of the second liquid outlet and move upward inside the first liquid outlet. At this time, the lubricating fluid can flow from one side of the baffle to the inner wall of the second liquid outlet, and finally flow out from the inner wall of the second liquid outlet to the top end of the grinding roller for lubrication.

[0021] The lubrication assembly works in conjunction with the cleaning head, which guides the lubricant when adding lubricant to the grinding roller tire. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 This is a schematic cross-sectional view of the overall structure of the present invention;

[0024] Figure 3 This is a schematic cross-sectional view of a partial structure of the present invention;

[0025] Figure 4 This is a schematic cross-sectional view of the internal structure of the coal mill body of the present invention;

[0026] Figure 5 This is a schematic cross-sectional view of the tripod structure of the present invention;

[0027] Figure 6 For the present invention Figure 3 Enlarged schematic diagram of the structure at point A in the middle;

[0028] Figure 7 For the present invention Figure 4 Enlarged schematic diagram of the structure at point B;

[0029] Figure 8 For the present invention Figure 5 Enlarged schematic diagram of the structure at point C;

[0030] Figure 9 For the present invention Figure 5 Enlarged schematic diagram of the structure at point D.

[0031] In the diagram: 1. Main body of the coal mill; 2. Drive structure; 3. Grinding disc; 4. Grinding roller; 5. Triangular frame; 6. Hydraulic tie rod; 7. First liquid outlet; 8. Baffle; 9. First connecting rod; 10. Second connecting rod; 11. First connecting plate; 12. Threaded rod; 13. First motor; 14. Fixing plate; 15. Second liquid outlet; 16. Sealing gasket; 17. Liquid filling hole; 18. Liquid filling plug; 19. Motor box; 20. Second motor; 21. First connecting shaft; 22. First gear; 23. Second gear; 24. Second connecting shaft; 25. First spring; 26. Connecting rope; 27. Protrusion; 29. ​​Fixing block; 30. Second connecting plate; 31. Connecting pipe; 32. Cleaning head; 33. Second spring; 34. Third connecting rod; 35. Third spring. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] like Figures 1 to 9As shown in the embodiment of the present invention, a bowl-type medium-speed coal mill roller device includes a coal mill body 1, a drive structure 2 installed at the bottom of the coal mill body 1, a grinding disc 3 arranged inside the coal mill body 1, a grinding roller 4 arranged above the grinding disc 3, multiple grinding rollers 4 are arranged, a cleaning component is arranged at the top of each grinding roller 4, each grinding roller 4 is fixedly installed at the bottom of a tripod 5, a lubrication component is arranged inside the tripod 5, and a hydraulic tie rod 6 is installed at the bottom of the tripod 5;

[0034] The cleaning component includes a cleaning head 32 disposed at the top of the grinding roller 4. The cleaning heads 32 are evenly distributed, and the top of each cleaning head 32 is slidably mounted on the inner wall of the connecting pipe 31. Each connecting pipe 31 is fixedly mounted on the bottom of the second connecting plate 30. The second connecting plate 30 is slidably mounted on the inner wall of the tripod 5 via a moving component.

[0035] By setting up the cleaning component, the grinding roller 4 can contact the bottom end of the cleaning head 32 during rotation. The cleaning head 32 cleans the surface of the grinding roller 4 tire, preventing the accumulation of dirt on the surface of the grinding roller 4 tire due to coal dust or other materials. This dirt may affect the normal operation of the grinding roller 4, thereby increasing the frictional resistance during equipment operation and indirectly affecting the safety of the equipment. Cleaning the surface of the grinding roller 4 tire not only helps to reduce the frictional resistance during equipment operation, but also helps to improve the safety of the equipment.

[0036] like Figure 4-9 As shown, the bottom end of the cleaning head 32 is tilted.

[0037] By tilting the bottom of the cleaning head 32 and gradually increasing the length of each cleaning head 32, the tilt angle of the grinding roller 4 tire is adapted to increase the contact area with the surface of the grinding roller 4 tire, thereby further improving the cleaning effect.

[0038] like Figure 1-9 As shown, the moving component includes a fixing block 29 fixedly installed on the top of the second connecting plate 30. A protrusion 27 is provided on one side of the fixing block 29. A connecting rope 26 is fixedly connected to one side of the protrusion 27. The end of the connecting rope 26 away from the protrusion 27 is installed on the outer wall of the second connecting shaft 24. A second gear 23 is fixedly installed on the outer wall of the second connecting shaft 24. A first gear 22 is meshed with one side of the second gear 23. A first connecting shaft 21 is fixedly connected to the inner wall of the first gear 22. A second motor 20 is fixedly connected to one end of the first connecting shaft 21. The second motor 20 is installed inside the motor box 19. The motor box 19 is fixedly installed on the side wall of the tripod 5.

[0039] By configuring the moving components, when cleaning the surface of the grinding roller 4 tire is required, the second motor 20 can be started by an external power source. Since the input end of the second motor 20 is electrically connected to the external power source via a wire, and the output end of the second motor 20 is fixedly connected to the first connecting shaft 21, starting the second motor 20 can drive the first connecting shaft 21 to rotate. The rotation of the first connecting shaft 21 drives the rotation of the first gear 22, which in turn drives the rotation of the second gear 23. The rotation of the second gear 23 unwinds the connecting rope 26, causing the protrusion 27 to move towards one side of the fixed block 29. Since the side of the protrusion 27 closest to the fixed block 29 is set as an inclined surface, the protrusion 27 contacts the fixed block 29, causing the fixed block 29 to slide to one side. The movement of the fixed block 29 drives the movement of the second connecting plate 30, which in turn drives the movement of the connecting tube 31. The movement of the connecting tube 31 drives the movement of the cleaning head 32, causing the cleaning head 32 to move at the top of the grinding roller 4 for cleaning, further improving the cleaning effect.

[0040] Each grinding roller 4 has a cleaning component at its top, and each cleaning component has a protrusion 27 on one side. Each protrusion 27 is fixedly connected to the others by a connecting rope 26, so that the cleaning components at the top of multiple grinding rollers 4 move synchronously.

[0041] like Figure 9 As shown, a second spring 33 is connected between the cleaning head 32 and the connecting tube 31.

[0042] By setting the second spring 33, when the cleaning head 32 moves, the elastic force of the second spring 33 can keep the bottom of the cleaning head 32 in contact with the surface of the grinding roller 4 tire. This prevents the cleaning head 32 from having a reduced contact area when moving and cleaning due to the tilting of the grinding roller 4 tire, thus ensuring the cleaning effect of the cleaning head 32 on the surface of the grinding roller 4 tire.

[0043] like Figure 8 As shown, the first gear 22 is configured as a sector gear.

[0044] The first gear 22 is configured as a sector gear. When the first gear 22 rotates and meshes with the second gear 23, it can drive the second gear 23 to rotate, so that the first gear 22 intermittently drives the second gear 23 to rotate. Through the cooperation of the first spring 25 and the third spring 35, the reciprocating movement of the cleaning component is realized.

[0045] like Figure 8 As shown, the second connecting shaft 24 is rotatably mounted on the inner wall of the tripod 5, and a first spring 25 is installed between the second connecting shaft 24 and the tripod 5.

[0046] With the first spring 25 in place, when the second connecting shaft 24 rotates, the first spring 25 deforms and stores elastic potential energy. When the first gear 22 and the second gear 23 are not meshed, the first spring 25 releases elastic potential energy to drive the second connecting shaft 24 to reverse, thereby winding up the connecting rope 26.

[0047] like Figure 7 and Figure 9 As shown, a third connecting rod 34 is fixedly connected to one side of the fixing block 29. The third connecting rod 34 is slidably installed on the inner wall of the tripod 5, and a third spring 35 is provided on the outer wall of the third connecting rod 34.

[0048] With the third connecting rod 34 slidably mounted on the inner wall of the tripod 5, the movement of the fixed block 29 is limited. With the third spring 35, when the protrusion 27 drives the fixed block 29 to move, the fixed block 29 compresses the third spring 35, causing the third spring 35 to deform and store elastic potential energy. When the side of the protrusion 27 separates from the fixed block 29, the elastic potential energy can be released by the third spring 35 to push the fixed block 29 to reset, thereby resetting the cleaning head 32 and causing the cleaning head 32 to reciprocate on the surface of the grinding roller 4 tire, further improving the cleaning effect.

[0049] like Figure 1-9 As shown, the lubrication assembly includes a first liquid outlet 7 opened inside the tripod 5. A baffle 8 is slidably installed inside the first liquid outlet 7. A first connecting rod 9 is fixedly installed at the top of the baffle 8. A second connecting rod 10 is fixedly connected to the top of the first connecting rod 9. A first connecting plate 11 is fixedly installed at the top of the second connecting rod 10. A threaded rod 12 is embedded in the inner wall of the first connecting plate 11. A first motor 13 is fixedly installed at the top of the threaded rod 12. The first motor 13 is fixedly installed on one side of a fixed plate 14. The fixed plate 14 is fixedly installed at the top of the tripod 5.

[0050] By configuring the lubrication components, when lubrication of the bowl-type medium-speed coal mill's roller 4 device is required, the threaded rod 12 is first started by an external power source. The start of the threaded rod 12 drives the first connecting plate 11 to move, which in turn drives the second connecting rod 10 to move. The movement of the second connecting rod 10 drives the first connecting rod 9 to move, which in turn drives the baffle 8 to move. This causes the bottom end of the baffle 8 to separate from the top end of the second liquid outlet 15 and move upward inside the first liquid outlet 7. At this time, the lubricating fluid can flow from one side of the baffle 8 to the inner wall of the second liquid outlet 15, and finally flow out from the inner wall of the second liquid outlet 15 to the top of the roller 4 for lubrication.

[0051] At the same time, it can also be used in conjunction with the cleaning head 32, so that when the device adds lubricant to the grinding roller 4 tire, the lubricant can be guided through the cleaning head 32, so that the lubricant can be evenly applied to the surface of the grinding roller 4 tire and the lubrication effect can be improved.

[0052] like Figure 7 As shown, a sealing gasket 16 is fixedly installed at the bottom of the baffle 8. The sealing gasket 16 is embedded in the inner wall of the second liquid outlet 15, which is located at the bottom of the first liquid outlet 7.

[0053] By setting the sealing gasket 16, after the liquid discharge is completed, the sealing gasket 16 can be embedded into the inner wall of the second liquid discharge hole 15 to seal it, effectively preventing lubricant leakage and improving the reliability of the equipment.

[0054] like Figure 1-3 As shown, a liquid filling hole 17 is provided inside the top of the tripod 5, and a liquid filling plug 18 is slidably installed inside the liquid filling hole 17.

[0055] With the addition of the lubricating component, when it is necessary to add lubricant to the inside of the tripod 5, the lubricant can be added to the inside of the tripod 5 by first pulling out the lubricating plug 18 and pouring the lubricant into the lubricating hole 17.

[0056] Working principle and usage process:

[0057] When the bowl-type medium-speed coal mill is working, the drive structure 2 consists of an electric motor and a reducer. The high-voltage electric motor provides the power source, driving the reducer to rotate. The grinding disc 3 is mounted on the reducer and rotates synchronously. On top of it are three grinding rollers 4, which are fixed on a tripod 5. The lifting and lowering are controlled by three hydraulic levers 6. The hydraulic pressure generated by the hydraulic cylinder is finally transmitted to the grinding rollers 4, generating grinding pressure with the grinding disc 3 to crush coal powder. When the coal mill stops running, the hydraulic levers 6 can also lift the tripod 5 and the grinding rollers 4, and the grinding pressure disappears, protecting the equipment.

[0058] If it is necessary to add lubricant to the inside of the tripod 5, the lubricant can first be added to the inside of the tripod 5 by pulling out the lubricant plug 18 and pouring the lubricant into the lubricant hole 17.

[0059] When lubrication of the bowl-type medium-speed coal mill roller 4 device is required, the threaded rod 12 is first started by external power. The start of the threaded rod 12 drives the first connecting plate 11 to move. The movement of the first connecting plate 11 drives the second connecting rod 10 to move. The movement of the second connecting rod 10 drives the first connecting rod 9 to move. The movement of the first connecting rod 9 drives the baffle 8 to move, so that the bottom end of the baffle 8 separates from the top end of the second liquid outlet 15 and moves upward inside the first liquid outlet 7. At this time, the lubricating fluid can flow from one side of the baffle 8 to the inner wall of the second liquid outlet 15, and finally flow out from the inner wall of the second liquid outlet 15 to the top end of the grinding roller 4 to lubricate it.

[0060] When cleaning the wheel-type grinding roller 4 of the bowl-type medium-speed coal mill is required, the second motor 20 is first started by an external power source. The start of the second motor 20 drives the rotation of the first connecting shaft 21, which in turn drives the rotation of the first gear 22. The rotation of the first gear 22 drives the rotation of the second gear 23, which unwinds the connecting rope 26 and moves the protrusion 27 toward one side of the fixed block 29. The protrusion 27 contacts the fixed block 29, causing the fixed block 29 to slide to one side. The movement of the fixed block 29 causes the second connecting plate 30 to move, which in turn causes the connecting pipe 31 to move. The movement of the connecting pipe 31 causes the cleaning head 32 to move, so that the cleaning head 32 moves at the top of the grinding roller 4. At the same time, the cleaning head 32 moves left and right to clean the top of the grinding roller 4 through the cooperation of the third spring 35 and the third connecting rod 34.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bowl-type medium-speed coal mill roller device, comprising a coal mill body (1), characterized in that: A drive structure (2) is installed at the bottom of the main body (1) of the coal mill. A grinding disc (3) is installed inside the main body (1). A grinding roller (4) is installed above the grinding disc (3). Multiple grinding rollers (4) are provided. A cleaning component is provided at the top of each grinding roller (4). Each grinding roller (4) is fixedly installed at the bottom of a tripod (5). A lubrication component is provided inside the tripod (5). A hydraulic pull rod (6) is installed at the bottom of the tripod (5). The cleaning component includes a cleaning head (32) installed at the top of the grinding roller (4). 32) The cleaning heads (32) are evenly distributed, with the top of each cleaning head (32) slidably mounted on the inner wall of the connecting tube (31). Each connecting tube (31) is fixedly mounted on the bottom of the second connecting plate (30). The second connecting plate (30) is slidably mounted on the inner wall of the tripod (5) via a moving assembly. The moving assembly includes a fixing block (29) fixedly mounted on the top of the second connecting plate (30). A protrusion (27) is provided on one side of the fixing block (29). A connecting rope (26) is fixedly connected to one side of the protrusion (27). The end of the connecting rope (26) away from the protrusion (27) is installed with... On the outer wall of the second connecting shaft (24), a second gear (23) is fixedly installed. A first gear (22) is meshed with one side of the second gear (23). A first connecting shaft (21) is fixedly connected to the inner wall of the first gear (22). A second motor (20) is fixedly connected to one end of the first connecting shaft (21). The second motor (20) is installed inside the motor box (19). The motor box (19) is fixedly installed on the side wall of the tripod (5). A second spring (33) is connected between the cleaning head (32) and the connecting tube (31). The first gear (22) is a sector gear, the second connecting shaft (24) is rotatably mounted on the inner wall of the tripod (5), a first spring (25) is installed between the second connecting shaft (24) and the tripod (5), a third connecting rod (34) is fixedly connected to one side of the fixing block (29), the third connecting rod (34) is slidably mounted on the inner wall of the tripod (5), a third spring (35) is provided on the outer wall of the third connecting rod (34), the lubrication assembly is used in conjunction with the cleaning head, and the lubricant is guided by the cleaning head when adding lubricant to the grinding roller tire.

2. The bowl-type medium-speed coal mill roller device according to claim 1, characterized in that: The bottom end of the cleaning head (32) is inclined.

3. The bowl-type medium-speed coal mill roller device according to claim 1, characterized in that: The lubrication assembly includes a first liquid outlet (7) opened inside the tripod (5), a baffle (8) is slidably installed inside the first liquid outlet (7), a first connecting rod (9) is fixedly installed at the top of the baffle (8), a second connecting rod (10) is fixedly connected to the top of the first connecting rod (9), a first connecting plate (11) is fixedly installed at the top of the second connecting rod (10), a threaded rod (12) is embedded in the inner wall of the first connecting plate (11), a first motor (13) is fixedly installed at the top of the threaded rod (12), the first motor (13) is fixedly installed on one side of a fixed plate (14), and the fixed plate (14) is fixedly installed at the top of the tripod (5).

4. The bowl-type medium-speed coal mill roller device according to claim 3, characterized in that: A sealing gasket (16) is fixedly installed at the bottom end of the baffle (8). The sealing gasket (16) is embedded in the inner wall of the second liquid outlet (15). The second liquid outlet (15) is located at the bottom end of the first liquid outlet (7).

5. The bowl-type medium-speed coal mill roller device according to claim 1, characterized in that: The top of the tripod (5) has a liquid filling hole (17) inside, and a liquid filling plug (18) is slidably installed inside the liquid filling hole (17).

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