Shaft sealing structure, gear box and wind turbine generator set

Abstract

The present disclosure relates to a shaft sealing structure, a gearbox and a wind turbine generator set, the gearbox comprising: a gearbox body having a through hole; a shaft connected with the gearbox body, and the shaft partially extends out of the gearbox body through the through hole; a sealing member sealing a gap between the shaft and an inner wall surface of the through hole; a fan connected with the shaft, the fan being arranged adjacent to the through hole, and the fan generates airflow following the rotation of the shaft, the airflow flowing at least in an axial direction of the shaft and away from the sealing member; wherein a spacing space is present between the sealing member and the fan inside the gearbox body, and the gearbox body is provided with a communication hole, and the spacing space is in communication with an external environment through the communication hole. The technical solution provided by the present disclosure can reduce the accumulation of oil at the sealing member and improve the sealing effect.

Description

Technical Field

[0001] This disclosure relates to the technical field of wind power equipment, and in particular to a shaft sealing structure, a gearbox, and a wind turbine generator set. Background Technology

[0002] The gearbox is a key component of a wind turbine generator set. Its main function is to increase the low speed of the wind turbine to the high speed required by the generator, thereby realizing the transmission and conversion of wind energy into electrical energy.

[0003] Most existing gearbox shaft sealing structures use sealing rings for sealing. However, due to the high temperature and high pressure inside the gearbox, oil inside the gearbox is prone to accumulate at the sealing ring, putting pressure on the sealing ring, affecting the sealing effect, and easily causing oil leakage problems. Utility Model Content

[0004] The purpose of this disclosure is to provide a shaft sealing structure, gearbox, and wind turbine generator set that can reduce oil accumulation at the seal and improve the sealing effect.

[0005] According to one aspect of this disclosure, a gearbox is provided, the gearbox comprising: a housing having a through hole; a shaft rotatably connected to the housing, the shaft portion extending out of the housing through the through hole; a seal sealing the gap between the shaft and the inner wall of the through hole; and a fan connected to the shaft, the fan being disposed adjacent to the through hole, the fan rotating with the shaft to generate airflow, the airflow flowing at least along the axial direction of the shaft in a direction away from the seal; wherein, the interior of the housing has a space between the seal and the fan, the housing having a connecting hole through which the space communicates with the external environment.

[0006] The technical solution provided in this disclosure involves installing a fan on a shaft. When the gearbox is running, the shaft rotates, and the fan rotates with the shaft. The fan generates an airflow toward the inside of the gearbox. This airflow can block the oil that would normally flow from inside the gearbox to the seal, thereby preventing the oil inside the gearbox from accumulating at the seal and improving the sealing effect.

[0007] Meanwhile, the housing is also equipped with a connecting hole that communicates with the partition space. Gas from the external environment can enter the partition space through this connecting hole, maintaining the air pressure within the partition space at or near the same as the external air pressure. Thus, during fan operation, the fan draws gas from the partition space, and the external environment is connected to the partition space through the connecting hole. This prevents external air from being forced into the gearbox due to low air pressure within the partition space, thus avoiding dust ingress. Furthermore, when the gearbox stops operating, the fan ceases operation, and the prolonged operation inside the gearbox leads to high internal temperature and increased air pressure. This high pressure can also be released through the connecting hole, preventing the oil inside the gearbox from being forced towards the seals and causing seal failure, thus ensuring a proper seal.

[0008] Optionally, the connecting hole is located at the upper part of the space.

[0009] With the above solution, when the oil flows into the partition space, the oil is located at the lower part of the partition space under the action of gravity. By setting the connecting hole at the upper part of the partition space, the oil can be prevented from flowing out through the connecting hole, reducing oil leakage and thus reducing the number of times the oil needs to be replenished.

[0010] Optionally, the connecting hole is located at the highest point of the space.

[0011] The above method can further reduce the possibility of oil flowing out through the connecting hole.

[0012] Optionally, a filter is installed in the passageway between the connecting hole and the external environment.

[0013] The above solution filters dust or foreign objects that enter the gearbox from the external environment through the connecting holes, ensuring the stable operation of the gearbox.

[0014] Optionally, the inner wall surface of the housing forms an annular groove extending radially outward along the shaft, and the connecting hole is located at the upper part of the annular groove.

[0015] The above solution can increase the distance between the connecting hole and the shaft by using the annular groove, thereby increasing the distance between the connecting hole and the oil flowing along the shaft, and further reducing the possibility of oil flowing out through the connecting hole.

[0016] Optionally, the fan is an axial fan; the airflow generated by the fan flows axially away from the seal along the shaft.

[0017] Optionally, the fan is a centrifugal fan; the airflow generated by the fan flows radially along the shaft and, guided by the channel formed by the inner wall of the housing and the fan, flows axially away from the seal along the shaft.

[0018] Optionally, the seal includes a base and a first contact portion; the base is annular and is disposed on the inner wall surface of the through hole; the first contact portion is annular, the outer edge of the first contact portion is connected to the inner wall surface of the base, the inner edge of the first contact portion is in contact with the circumferential surface of the shaft, and the first contact portion bends and extends away from the fan.

[0019] With the above solution, when the air pressure inside the space is low, the air pressure of the external environment can press the first contact part tightly, increasing the pressure and contact area between the first contact part and the circumferential surface of the shaft, thereby improving the sealing effect.

[0020] Optionally, the seal further includes a second contact portion; the second contact portion is located between the first contact portion and the fan, and the first contact portion and the second contact portion are arranged symmetrically.

[0021] With the above solution, when the air pressure inside the space is high, the air pressure inside the space can press the second contact part tightly, increasing the pressure and contact area between the second contact part and the circumferential surface of the shaft, thereby improving the sealing effect.

[0022] Optionally, the housing includes a main body and a transparent cover connected to the main body, the shaft is rotatably connected to the main body, and the through hole and the connecting hole are formed on the transparent cover.

[0023] The above method allows for the first removal of the through cover to create a sufficiently large opening. The fan-connected shaft is then installed on the main body, and finally, the through cover is reinstalled, facilitating the assembly of the fan-connected shaft into the housing. Furthermore, the through cover is relatively small compared to the main body, and the through holes and connecting holes are located on the through cover, simplifying the machining of these holes.

[0024] According to another aspect of this disclosure, a wind turbine generator set is provided, the wind turbine generator set including the aforementioned gearbox.

[0025] The above solutions can reduce oil leakage from the gearbox, improve the stability and reliability of wind turbine operation, and reduce the need for oil replenishment and cleaning maintenance.

[0026] According to another aspect of this disclosure, a shaft sealing structure is provided, the shaft sealing structure comprising: a through cover having a through hole; a shaft partially passing through the through hole; a seal sealing the gap between the shaft and the inner wall of the through hole; and a fan connected to the shaft, the fan being disposed adjacent to the through hole, the fan rotating with the shaft to generate airflow, the airflow flowing at least along the axial direction of the shaft in a direction away from the seal; wherein, the interior of the through cover is located between the seal and the fan, the through cover having a connecting hole, the connecting hole communicating with the external environment.

[0027] By adopting the above solution, the equipment using this shaft sealing structure can improve the sealing effect at the shaft end and reduce the possibility of oil leakage. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A partial half-sectional schematic diagram of a gearbox according to an embodiment of the present disclosure is shown;

[0030] Figure 2 It shows Figure 1 Enlarged diagram of part A in the diagram;

[0031] Figure 3 A half-sectional schematic diagram of a seal according to an embodiment of the present disclosure is shown.

[0032] Explanation of reference numerals in the attached figures:

[0033] 100. Box body; 101. Through hole; 102. Annular groove; 110. Main body; 120. Through cover;

[0034] 200. Shaft components;

[0035] 300, Seal; 310, Base; 320, First Contact; 330, Second Contact;

[0036] 400. Fan;

[0037] 500, Spacing; 510, Connecting hole. Detailed Implementation

[0038] As the core transmission component of a wind turbine generator, the gearbox's core function is to efficiently convert the low-speed, high-torque power generated by the wind turbine's capture of wind energy into the high-speed, low-torque power required for generator power generation. It is a crucial hub for achieving efficient wind energy to electrical energy conversion. In current mainstream gearbox designs, shaft sealing structures generally employ ring seals. However, during gearbox operation, the internal temperature remains high due to mechanical transmission heat, creating a high-pressure environment. Under these conditions, the lubricating and cooling oil inside the gearbox tends to accumulate in the sealing ring area, continuously applying additional pressure to the seal. This phenomenon not only accelerates the aging and deformation of the seal, leading to a gradual decline in its sealing performance, but also easily causes oil leakage at the shaft seals. In severe cases, this directly affects the gearbox's operational stability and the generator's power generation efficiency.

[0039] Based on this, this disclosure attempted to install a fan inside the gearbox and connect the fan to the shaft. In this way, when the gearbox is running, the fan can rotate with the shaft, and the fan can generate airflow toward the inside of the gearbox, thereby using the airflow to prevent oil inside the gearbox from accumulating at the seal.

[0040] Meanwhile, considering that during fan operation, the fan constantly draws air from between the fan and the sealing ring, creating a low-pressure area between them, external air can easily force the sealing ring into the gearbox, leading to dust ingress. Additionally, when the gearbox stops running, the fan stops operating, and the prolonged operation inside the gearbox results in high internal temperature and increased air pressure, which also creates a high-pressure area inside the gearbox. This causes the oil inside the gearbox to be forced against the sealing ring, resulting in seal failure.

[0041] To this end, this disclosure further provides a connecting hole between the fan and the sealing ring. The area between the fan and the sealing ring is connected to the external environment through the connecting hole, so that the air pressure is balanced by the connecting hole, so as to make the sealing on both sides of the sealing ring as even as possible, and further ensure the sealing effect.

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this disclosure, but not all embodiments.

[0043] like Figure 1 and Figure 2As shown, this disclosure provides a gearbox that can be used in wind turbine generator sets. Its core function is to connect the wind turbine and the generator, effectively converting the low speed generated by the wind turbine capturing wind energy into the high speed required by the generator to generate electricity through mechanical transmission, thereby ensuring the efficient operation of the generator set. Of course, the gearbox can also be used in other equipment that requires high / low speed regulation or torque regulation, and is not specifically limited here.

[0044] Specifically, the gearbox may include a housing 100 and a shaft 200. The housing 100, as the main structure of the gearbox, primarily supports and protects other components. The housing 100 has a through hole 101. The shaft 200 is rotatably connected to the housing 100, and the through hole 101 connects the interior of the housing 100 to the external environment, allowing the shaft 200 inside the housing 100 to extend outwards; that is, a portion of the shaft 200 extends out of the housing 100 through the through hole 101. For example, the shaft 200 may be a high-speed shaft or a low-speed shaft on the gearbox, and the portion of the shaft 200 extending out of the through hole 101 is used to connect with other components to transmit speed and torque.

[0045] The gearbox may also include a seal 300 and a fan 400. The seal 300 seals the gap between the shaft 200 and the inner wall of the through hole 101 to prevent oil leakage from inside the gearbox 100 through this gap, and to prevent dust from the external environment from entering the gearbox 100 through the gap between the shaft 200 and the inner wall of the through hole 101. The fan 400 is located inside the gearbox 100 and connected to the shaft 200. The fan 400 is positioned adjacent to the through hole 101 and rotates with the shaft 200 to generate airflow. The airflow flows at least along the axial direction of the shaft 200 in a direction away from the seal 300. In this way, when the gearbox is running, the shaft 200 rotates, and the fan 400 rotates with the shaft 200. The fan 400 generates airflow toward the inside of the gearbox. This airflow can block the oil that originally flowed from inside the gearbox to the seal 300, thereby using the airflow to prevent the oil inside the gearbox from accumulating at the seal 300 and improving the sealing effect.

[0046] Furthermore, the interior of the enclosure 100 contains a space 500 between the seal 300 and the fan 400; or, the space inside the enclosure 100 between the seal 300 and the fan 400 is defined as the space 500. The enclosure 100 is provided with a connecting hole 510, through which the space 500 communicates with the external environment. In this way, gas from the external environment can enter the space 500 through the connecting hole 510, and the connecting hole 510 can maintain the air pressure inside the space 500 at or near the same level as the air pressure in the external environment. Thus, during the operation of fan 400, fan 400 draws gas from the space 500. The external environment is connected to the space 500 through the connecting hole 510. The connecting hole 510 can prevent external air from forcing the seal 300 into the gearbox due to low air pressure in the space 500, thereby causing dust to enter. Also, when the gearbox stops running, fan 400 stops operating. The long-term operation of the gearbox leads to high internal temperature and increased air pressure, which will also generate high pressure inside the gearbox. At this time, the high pressure can be released through the connecting hole 510, preventing the oil inside the gearbox from being forced to the seal 300 and causing the seal 300 to fail, thus ensuring the sealing effect.

[0047] In some embodiments, the connecting hole 510 may be located at the upper part of the space 500. In this way, when the oil flows into the space 500, the oil is located at the lower part of the space 500 under the action of gravity. By placing the connecting hole 510 at the upper part of the space 500, the oil can be prevented from flowing out through the connecting hole 510, reducing oil leakage and thus reducing the frequency of oil replenishment.

[0048] Furthermore, the connecting hole 510 can be located at the highest point of the space 500, further reducing the possibility of oil flowing out through the connecting hole 510.

[0049] To reduce the possibility of dust or foreign objects from the external environment entering the housing 100 through the connecting hole 510, in some embodiments, a filter (not shown) is installed on the passage between the connecting hole 510 and the external environment, so that the filter can filter dust or foreign objects from the external environment entering the housing 100 through the connecting hole 510, thereby ensuring the stable operation of the gearbox.

[0050] In some embodiments, such as Figure 2 As shown, the inner wall surface of the housing 100 forms an annular groove 102 extending radially outward along the shaft 200, and the connecting hole 510 is located at the upper part of the annular groove 102. In this way, the annular groove 102 can be used to increase the distance between the connecting hole 510 and the shaft 200, thereby increasing the distance between the connecting hole 510 and the oil flowing along the shaft 200, further reducing the possibility of oil flowing out through the connecting hole 510.

[0051] Regarding the specific structure of the fan 400, this disclosure provides two embodiments for reference.

[0052] Example 1: The fan 400 described above can be an axial flow fan. That is, when the fan 400 is running, the airflow generated by the fan 400 flows along the axial direction of the fan 400 in a direction away from the seal 300, that is, along the axial direction of the shaft 200 in a direction away from the seal 300.

[0053] Example 2, as follows Figure 2 As shown, the fan 400 can be a centrifugal fan. The airflow generated by the fan 400 flows radially along the shaft 200, and under the guidance of the channel formed by the inner wall of the housing 100 and the fan 400, it flows axially along the shaft 200 in a direction away from the seal 300 (see [reference]). Figure 2 (As indicated by the arrow), thus preventing the oil from approaching the seal at 300.

[0054] For example, a receiving groove may be formed on the inner wall surface of the housing 100, and the fan 400 is partially located in the receiving groove. There is at least a predetermined distance between the outer edge of the fan 400 and the bottom of the receiving groove, and between the back of the fan 400 and the side wall of the receiving groove, to form a channel for airflow.

[0055] In some embodiments, such as Figure 2 and Figure 3 As shown, the seal 300 includes a base 310 and a first contact portion 320. The base 310 serves as the main support portion of the seal 300. The base 310 is annular and is disposed on the inner wall surface of the through hole 101 to define the installation position of the seal 300. For example, the cross-section of the base 310 can be rectangular or L-shaped. A groove may be provided on the inner wall surface of the through hole 101, and the base 310 is installed within the groove to restrict the axial movement of the seal 300 and ensure the installation stability of the seal 300.

[0056] The first contact portion 320 is annular, with its outer edge connected to the inner wall of the base 310 and its inner edge in contact with the circumferential surface of the shaft 200. The first contact portion 320 also bends and extends away from the fan 400. Thus, when the air pressure inside the space 500 is low, the air pressure from the external environment can compress the first contact portion 320, increasing the pressure and contact area between the first contact portion 320 and the circumferential surface of the shaft 200, thereby improving the sealing effect.

[0057] Furthermore, the seal 300 also includes a second contact portion 330. The second contact portion 330 is located between the first contact portion 320 and the fan 400, and the first contact portion 320 and the second contact portion 330 are arranged symmetrically. That is, the outer edge of the second contact portion 330 is connected to the base 310, the inner edge of the second contact portion 330 contacts the circumferential surface of the shaft 200, and the second contact portion 330 bends and extends towards the fan 400. In this way, when the air pressure inside the partition space 500 is high, the air pressure inside the partition space 500 can press the second contact portion 330 tightly, increasing the pressure and contact area between the second contact portion 330 and the circumferential surface of the shaft 200, thereby improving the sealing effect.

[0058] In some embodiments, such as Figure 1 As shown, the housing 100 may include a main body 110 and a through cover 120 connected to the main body 110. A shaft 200 is rotatably connected to the main body 110. A through hole 101 and a connecting hole 510 are formed on the through cover 120. That is, the through cover 120 is detachably connected to the main body 110. The through cover 120 can be manufactured as an independent unit, or it can be integrally installed on or detached from the main body 110. Thus, the through cover 120 can be removed first to obtain a sufficiently large opening, then the shaft 200 connected to the fan 400 can be installed on the main body 110, and finally the through cover 120 can be installed to facilitate the assembly of the shaft 200 connected to the fan 400 inside the housing 100. Simultaneously, the through cover 120 is relatively small in volume compared to the main body 110, and the through hole 101 and connecting hole 510 are formed on the through cover 120, facilitating the machining operations of the through hole 101 and connecting hole 510.

[0059] For example, the cover 120 and the body 110 can be connected by bolts to facilitate subsequent maintenance and replacement. Of course, the cover 120 and the body 110 can also be welded together.

[0060] Based on the same inventive concept, this disclosure also provides a wind turbine generator set, which includes the gearbox described above.

[0061] It should be noted that the specific structure of the gearbox can be found in the detailed description in the above embodiments, and will not be repeated here.

[0062] Based on the same inventive concept, this disclosure also provides a shaft sealing structure, which includes: a through cover 120 having a through hole 101; a shaft 200 partially passing through the through hole 101; a seal 300 sealing the gap between the shaft 200 and the inner wall of the through hole 101; and a fan 400 connected to the shaft 200, the fan 400 being disposed adjacent to the through hole 101, the fan 400 rotating with the shaft 200 to generate airflow, the airflow flowing at least along the axial direction of the shaft 200 in a direction away from the seal 300; wherein, the interior of the through cover 120 is located between the seal 300 and the fan 400, the through cover 120 is provided with a connecting hole 510, and the connecting hole 510 communicates with the external environment.

[0063] It should be noted that the specific structures of the cover 120, shaft 200, seal 300, and fan 400 can be found in the descriptions in the above embodiments. This shaft sealing structure can be used not only in the gearboxes described above, but also in other equipment that requires sealing of the shaft ends to prevent oil leakage, such as pump bodies and spindle boxes.

[0064] The terms "upper" and "lower" used in this disclosure are used to describe the relative positional relationship of the various structures in the accompanying drawings. They are only for the purpose of clarity of description and are not intended to limit the scope of implementation of this disclosure. Changes or adjustments to the relative relationships without substantially altering the technical content should also be considered as part of the scope of implementation of this disclosure.

[0065] It should be noted that, in this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0066] Furthermore, in this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A gearbox, characterized in that, The gearbox includes: A housing (100) having a through hole (101); A shaft (200) is rotatably connected to the housing (100), and a portion of the shaft (200) extends out of the housing (100) through the through hole (101); A seal (300) seals the gap between the shaft (200) and the inner wall of the through hole (101); A fan (400) is connected to the shaft (200). The fan (400) is disposed adjacent to the through hole (101). The fan (400) rotates with the shaft (200) to generate airflow. The airflow flows at least along the axial direction of the shaft (200) in a direction away from the seal (300). The interior of the housing (100) has a space (500) between the seal (300) and the fan (400). The housing (100) is provided with a connecting hole (510), and the space (500) is connected to the external environment through the connecting hole (510).

2. The gearbox according to claim 1, characterized in that, The connecting hole (510) is located at the upper part of the space (500).

3. The gearbox according to claim 2, characterized in that, The connecting hole (510) is located at the highest point of the space (500).

4. The gearbox according to claim 2, characterized in that, A filter is installed in the passageway between the connecting hole (510) and the external environment.

5. The gearbox according to claim 2, characterized in that, The inner wall of the housing (100) forms an annular groove (102) extending radially outward along the shaft (200), and the connecting hole (510) is located at the upper part of the annular groove (102).

6. The gearbox according to any one of claims 1 to 5, characterized in that, The fan (400) is an axial flow fan; The airflow generated by the fan (400) flows along the axial direction of the shaft (200) in a direction away from the seal (300).

7. The gearbox according to any one of claims 1 to 5, characterized in that, The fan (400) is a centrifugal fan; The airflow generated by the fan (400) flows radially along the shaft (200) and, guided by the channel formed by the inner wall of the housing (100) and the fan (400), flows axially away from the seal (300) along the shaft (200).

8. The gearbox according to claim 1, characterized in that, The seal (300) includes a base (310) and a first contact portion (320); The base (310) is annular and is disposed on the inner wall surface of the through hole (101); The first contact portion (320) is annular, the outer edge of the first contact portion (320) is connected to the inner wall surface of the base (310), the inner edge of the first contact portion (320) is in contact with the circumferential surface of the shaft (200), and the first contact portion (320) extends in a direction away from the fan (400).

9. The gearbox according to claim 8, characterized in that, The seal (300) also includes a second contact portion (330); The second contact portion (330) is located between the first contact portion (320) and the fan (400), and the first contact portion (320) and the second contact portion (330) are arranged symmetrically.

10. The gearbox according to claim 1, characterized in that, The housing (100) includes a main body (110) and a through cover (120) connected to the main body (110). The shaft (200) is rotatably connected to the main body (110). The through hole (101) and the connecting hole (510) are formed on the through cover (120).

11. A wind turbine generator set, characterized in that, The wind turbine generator set includes the gearbox according to any one of claims 1 to 10.

12. A shaft sealing structure, characterized in that, The shaft sealing structure includes: A through cover (120) having a through hole (101); A shaft (200) partially passes through the through hole (101); A seal (300) seals the gap between the shaft (200) and the inner wall of the through hole (101); A fan (400) is connected to the shaft (200). The fan (400) is disposed adjacent to the through hole (101). The fan (400) rotates with the shaft (200) to generate airflow. The airflow flows at least along the axial direction of the shaft (200) in a direction away from the seal (300). The inside of the transparent cover (120) is located between the sealing element (300) and the fan (400) with a space (500). The transparent cover (120) is provided with a connecting hole (510), and the space (500) is connected to the external environment through the connecting hole (510).

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